WEBVTT NOTE Created by CaptionSync from Automatic Sync Technologies www.automaticsync.com 00:00:00.036 --> 00:00:07.636 align:middle So excellent, excellent. 00:00:08.736 --> 00:00:10.126 align:middle Thank you all for being here. 00:00:10.896 --> 00:00:14.576 align:middle Um, do you know this is a large conference and you know, 00:00:14.576 --> 00:00:16.446 align:middle when you're organizing a large conference like this, 00:00:16.506 --> 00:00:18.756 align:middle you do want to have the best speakers, right? 00:00:19.576 --> 00:00:22.166 align:middle So, and what do you usually do when you're having a conference? 00:00:22.166 --> 00:00:26.806 align:middle You put the best speakers upfront, like the keynote is obviously the most impressive one 00:00:26.806 --> 00:00:30.196 align:middle and then you have the best speakers and then they slowly decline. 00:00:31.776 --> 00:00:36.986 align:middle Um, as you know, Michelle is not here, Michelle was about to do this talk so 00:00:36.986 --> 00:00:41.926 align:middle and her kid got sick and you can't really leave a two year old home in Switzerland by itself. 00:00:41.956 --> 00:00:42.886 align:middle So she had to stay home. 00:00:43.006 --> 00:00:45.956 align:middle So the conference organizers thought, Hey, what should we do? 00:00:46.126 --> 00:00:46.736 align:middle Michelle is sick. 00:00:46.736 --> 00:00:48.936 align:middle So obviously they did the best thing they could. 00:00:48.936 --> 00:00:51.066 align:middle They call the second best speaker, right? 00:00:53.286 --> 00:00:56.456 align:middle Unfortunately that person couldn't make it. 00:00:57.516 --> 00:01:01.846 align:middle So they called the most knowledgeable speaker who knows the Workflow component the best, 00:01:02.706 --> 00:01:04.476 align:middle and that person didn't make it either. 00:01:05.346 --> 00:01:09.166 align:middle Um, however, like five or six calls down the line, they find my name 00:01:09.486 --> 00:01:12.666 align:middle and here I am and I hope I can give you. 00:01:12.916 --> 00:01:13.826 align:middle Yeah, thank you. 00:01:18.146 --> 00:01:20.356 align:middle At least one guy or girl is very polite. 00:01:20.356 --> 00:01:26.776 align:middle I hope I could give you like a, a talk that could match Michelle's talk. 00:01:27.876 --> 00:01:36.576 align:middle So with uh, with that said, my talk is titled Knowing Your State Machines and I would 00:01:36.576 --> 00:01:40.506 align:middle like to do this talk because I believe web developers only care 00:01:40.506 --> 00:01:43.056 align:middle about printing out HTML as quick as possible. 00:01:43.416 --> 00:01:47.176 align:middle They don't care about fancy algorithms, they don't care about design patterns. 00:01:47.506 --> 00:01:49.306 align:middle They just want to print stuff really, really quick. 00:01:50.326 --> 00:01:53.776 align:middle And so I want to tell you about something that makes your code a little bit more elegant. 00:01:54.936 --> 00:01:58.236 align:middle So I didn't, I didn't bring any state machines. 00:01:58.886 --> 00:02:00.556 align:middle It's nothing I can have in my pocket. 00:02:01.506 --> 00:02:06.616 align:middle It's a state machine is just something that hold states, like any states. 00:02:07.316 --> 00:02:11.566 align:middle It could be the state of a pull request or this small washer 00:02:11.566 --> 00:02:13.396 align:middle on your - small lights on your washer. 00:02:14.056 --> 00:02:16.206 align:middle It could be, yeah, it could be anything. 00:02:16.206 --> 00:02:19.966 align:middle So it's basically a way of thinking, a way to relate to problems. 00:02:21.246 --> 00:02:22.746 align:middle And why state machines? 00:02:22.746 --> 00:02:23.166 align:middle Blah Blah. 00:02:23.166 --> 00:02:24.156 align:middle There's a lot of texts in this. 00:02:24.156 --> 00:02:27.916 align:middle If you work at a company where your manager needs convincing, this is a slide - 00:02:27.916 --> 00:02:29.556 align:middle just to take a photo or show him later. 00:02:30.386 --> 00:02:33.576 align:middle I'm sorry, show him or her later. 00:02:35.256 --> 00:02:36.046 align:middle Quick about me. 00:02:36.086 --> 00:02:38.296 align:middle I do plenty of work on Happyr. 00:02:38.296 --> 00:02:41.726 align:middle We are a job advert platform - it matches people with confidence, blah blah. 00:02:41.806 --> 00:02:43.426 align:middle I do plenty of Symfony things. 00:02:43.536 --> 00:02:47.866 align:middle I run PHP meetups in Stockholm and I do plenty of open source. 00:02:48.636 --> 00:02:55.576 align:middle I started my real open source career in 2015 on a SymfonyCon, just like this one. 00:02:55.846 --> 00:02:57.726 align:middle The PSR-6 cache had just came out. 00:02:58.076 --> 00:03:00.626 align:middle So me and my friends were like, hey, why don't we implement this. 00:03:01.006 --> 00:03:03.146 align:middle Why don't we make an implementation of PSR-6. 00:03:03.426 --> 00:03:04.466 align:middle So we did. 00:03:04.756 --> 00:03:09.246 align:middle We created the PHP-cache organization and CacheBundle and I thought open source is great. 00:03:09.576 --> 00:03:14.476 align:middle So I started to get involved with HTTPPlug, which is kind of an abstraction 00:03:14.476 --> 00:03:20.136 align:middle over HTTP clients and when you do HTTP clients, you do API clients and then you do mail clients. 00:03:20.626 --> 00:03:23.806 align:middle And I even wrote like, Oh, this is how you should do API clients, 00:03:23.806 --> 00:03:25.366 align:middle this is the boilerplate for FIG. 00:03:25.866 --> 00:03:28.906 align:middle And currently I'm maintaining both Guzzle and Buzz. 00:03:29.116 --> 00:03:33.076 align:middle I've written my PSR-7, I've written PSR standards and stuff. 00:03:33.076 --> 00:03:34.506 align:middle I, I do plenty of things. 00:03:36.026 --> 00:03:41.236 align:middle The most interesting library here, which I like the most is this one, the NSA one. 00:03:42.296 --> 00:03:48.606 align:middle With NSA, you can totally violate class privacy: accessing private properties 00:03:48.656 --> 00:03:54.456 align:middle or methods is super easy with NSA, I do also contribute to a bunch of other libraries: 00:03:55.116 --> 00:03:56.286 align:middle these are only the most fun ones. 00:03:56.936 --> 00:04:00.656 align:middle So how should we do this about state machine? 00:04:00.656 --> 00:04:02.586 align:middle How should we do this? 00:04:02.736 --> 00:04:08.016 align:middle I would like to start with a lot of theory and then l will put on some examples, 00:04:08.016 --> 00:04:09.406 align:middle examples, and then more examples. 00:04:10.106 --> 00:04:14.126 align:middle How does that sound? 00:04:14.566 --> 00:04:14.886 align:middle Excellent. 00:04:14.886 --> 00:04:17.546 align:middle Because I've got slides for this. 00:04:17.716 --> 00:04:22.996 align:middle How I can barely see you, but how many of you, how many of you feel 00:04:22.996 --> 00:04:24.566 align:middle like you know, state machines by heart? 00:04:27.336 --> 00:04:27.846 align:middle Excellent. 00:04:27.846 --> 00:04:31.466 align:middle It's like 12 of you, which, which is excellent. 00:04:32.716 --> 00:04:35.496 align:middle Then I guess like the rest of you will learn plenty. 00:04:36.586 --> 00:04:38.226 align:middle You are.. anyhow, let's get started. 00:04:38.226 --> 00:04:40.666 align:middle Let's get: first rule of state machines. 00:04:40.736 --> 00:04:43.886 align:middle We've got to talk about the graph theory and the first rule of graph theory is 00:04:43.886 --> 00:04:48.966 align:middle like these, these are not graphs. 00:04:49.106 --> 00:04:52.536 align:middle These are charts, these are diagrams, these are call them whatever. 00:04:52.746 --> 00:04:54.036 align:middle They are not graphs. 00:04:54.726 --> 00:04:59.186 align:middle A graph. It looks like this. 00:04:59.726 --> 00:05:00.966 align:middle A graph has a node. 00:05:02.086 --> 00:05:07.326 align:middle A more interesting graph got two nodes, and nodes can be connected with edges 00:05:08.236 --> 00:05:12.746 align:middle and edges can either be undirected like this one or it can be directed. 00:05:13.356 --> 00:05:19.456 align:middle An edge can also have a weight. 00:05:19.606 --> 00:05:21.626 align:middle Does this seem familiar for most of you? 00:05:22.996 --> 00:05:23.506 align:middle Excellent. 00:05:23.846 --> 00:05:24.206 align:middle Excellent. 00:05:24.996 --> 00:05:30.406 align:middle This is a full-fledged graph. 00:05:30.756 --> 00:05:32.836 align:middle This is like the cool graphs can be. 00:05:33.446 --> 00:05:37.436 align:middle And it can represent pretty much whatever thing you like it to represent. 00:05:38.256 --> 00:05:44.086 align:middle If you slap on some numbers on here and maybe you can have a problem, 00:05:44.186 --> 00:05:47.946 align:middle maybe this represents cities and roads between them. 00:05:48.186 --> 00:05:53.556 align:middle Maybe it represents computers in the network, maybe, maybe they represent people 00:05:53.556 --> 00:05:54.906 align:middle and how well they know each other. 00:05:54.906 --> 00:05:59.316 align:middle And say we've got a graph like this and you wonder how much.... 00:05:59.316 --> 00:06:01.746 align:middle say they are computers in the network. 00:06:02.176 --> 00:06:04.286 align:middle How much data can you transfer from a to b? 00:06:05.236 --> 00:06:08.646 align:middle This might be a problem you're having, 00:06:08.646 --> 00:06:13.166 align:middle so this is called the maximum flow problem and there is a solution to this. 00:06:13.476 --> 00:06:17.076 align:middle And say that you want to find the shorter distance between a 00:06:17.226 --> 00:06:21.376 align:middle and b. You can solve this this by Birpartite breadth-first search. 00:06:22.216 --> 00:06:24.026 align:middle And say that you want to... 00:06:24.906 --> 00:06:31.186 align:middle Say that you want to find out what's the cheapest way of visiting all these cities, 00:06:31.416 --> 00:06:34.776 align:middle or these nodes, visiting only every node once. 00:06:35.126 --> 00:06:38.176 align:middle That's a traveling salesman problem and there is a solution to that as well. 00:06:38.866 --> 00:06:43.236 align:middle Or say that these are cities and you should put out some electricity grid between them. 00:06:43.236 --> 00:06:47.416 align:middle This is the minimum spanning tree problem and there's a solution for that as well. 00:06:47.416 --> 00:06:52.566 align:middle What I want to tell you is if you've got a problem, if you can express this problem 00:06:52.566 --> 00:06:56.576 align:middle as a graph problem, there's already a solution to it. 00:06:56.576 --> 00:06:58.826 align:middle So you don't, you don't really have to solve these problems yourself, 00:06:58.826 --> 00:07:01.916 align:middle you can just solve the problem getting your problem to a graph problem. 00:07:02.736 --> 00:07:03.276 align:middle Does it make sense? 00:07:04.616 --> 00:07:05.166 align:middle Thank you. 00:07:05.526 --> 00:07:12.526 align:middle This, what I just did, I gave you like six months of university math of graphs. 00:07:12.896 --> 00:07:16.566 align:middle So this is basically the big graph theory I just gave you a quick introduction of. 00:07:17.516 --> 00:07:21.156 align:middle A cool thing about graphs is that you can reduce them. 00:07:22.436 --> 00:07:23.516 align:middle Say, consider this graph. 00:07:23.946 --> 00:07:27.686 align:middle I want to reduce them by giving them a new rule. 00:07:28.066 --> 00:07:33.926 align:middle And say, the rule might be: let's remove all the loops. 00:07:34.726 --> 00:07:39.356 align:middle If I remove all the loops in this graph, I get a tree. 00:07:40.386 --> 00:07:43.286 align:middle And there's plenty of algorithms you can do in trees as well. 00:07:43.736 --> 00:07:47.786 align:middle One of the most difficult to implement is the red then black search tree, 00:07:48.406 --> 00:07:50.946 align:middle which basically is good way to store things if you want to search quickly in it. 00:07:51.536 --> 00:07:53.156 align:middle Anyhow, I want to show you this. 00:07:53.156 --> 00:07:59.006 align:middle You have the big graph theory and inside of it you have the theory of a tree. 00:08:00.006 --> 00:08:02.466 align:middle And you can continue reducing graphs with different set 00:08:02.466 --> 00:08:05.606 align:middle of rules and you will get a workflow. 00:08:07.926 --> 00:08:15.416 align:middle A workflow also has nodes, but sorry, but we decided, oh also has nodes and it also has edges 00:08:15.416 --> 00:08:18.436 align:middle and we decided that every edge should be directed. 00:08:18.816 --> 00:08:22.186 align:middle We also decided that we call the nodes places and transitions. 00:08:23.446 --> 00:08:28.376 align:middle And a rule in this workflow is them saying: a place can never be connected to another place. 00:08:28.606 --> 00:08:32.386 align:middle All of this has to be a transition between them. 00:08:32.386 --> 00:08:38.686 align:middle I know I'm shooting a lot of rules at you now, but do you kind of feel comfortable? 00:08:39.436 --> 00:08:40.056 align:middle Excellent. 00:08:40.056 --> 00:08:44.386 align:middle And we decided, I mean just so it's easy to see, we draw these transitions like a square 00:08:45.346 --> 00:08:51.616 align:middle and a good example of a workflow is this: if I'm in place A and execute the transition t0, 00:08:51.616 --> 00:08:58.976 align:middle I'll get to place C. If I'm in place B and they execute the transition t1, 00:08:58.976 --> 00:09:04.346 align:middle I get to place C and D. Make sense? 00:09:06.616 --> 00:09:14.616 align:middle Good. If we continue to reduce this workflow, say we want to add rules saying 00:09:15.026 --> 00:09:22.146 align:middle that a transition could only have one input and one output and also the names has to be unique. 00:09:23.556 --> 00:09:28.596 align:middle Then we actually get a state machine that looks something like this. 00:09:28.766 --> 00:09:33.116 align:middle So workflow multiple one input, multiple outputs. 00:09:33.556 --> 00:09:36.776 align:middle A state machine only can have one input and one output, something like this. 00:09:37.046 --> 00:09:43.936 align:middle So if execute t1, if you are in B and execute t1 you get to D. 00:09:44.116 --> 00:09:48.146 align:middle And because I'm drawing these images by hand, I will choose to draw with this annotation. 00:09:50.106 --> 00:09:56.906 align:middle Fair? So right now I have been talking for eight minutes and we discussed the big graph theory 00:09:57.416 --> 00:10:01.656 align:middle and we discussed the tree and we discussed what a workflow is 00:10:01.656 --> 00:10:04.306 align:middle and that a state machine is just a reduced workflow. 00:10:04.306 --> 00:10:08.046 align:middle So let's start with some examples. 00:10:08.376 --> 00:10:11.866 align:middle I mean I know this part was the boring part, this part was the theory part. 00:10:11.866 --> 00:10:14.456 align:middle Let's start with some examples of recognize that we recognize. 00:10:15.046 --> 00:10:17.656 align:middle This is a simple state machine. 00:10:18.776 --> 00:10:24.856 align:middle We defined three states and we defined how we can move between the states, right? 00:10:24.966 --> 00:10:28.466 align:middle So it's easy to see that if you are in green we can easily move to yellow 00:10:28.466 --> 00:10:29.636 align:middle and then we can easily move to read. 00:10:30.456 --> 00:10:33.886 align:middle However though if we are in green, we cannot move to red. 00:10:34.436 --> 00:10:35.446 align:middle There's no arrow to red. 00:10:35.446 --> 00:10:40.046 align:middle It's impossible to go direct to red, which is which is a good thing. 00:10:40.556 --> 00:10:46.496 align:middle I've got to keep asking you simple questions until you give me some continuous feedback. 00:10:46.816 --> 00:10:48.026 align:middle Do you understand this? 00:10:48.786 --> 00:10:56.126 align:middle I work at a company called Happyr and we deal with a lot of job adverts. 00:10:56.126 --> 00:11:00.016 align:middle Basically we put up adverts and we match people and people in common with soft skills, etc, 00:11:00.016 --> 00:11:02.046 align:middle etc. Anyhow, we have a lot of job adverts. 00:11:02.426 --> 00:11:08.366 align:middle So in a business meeting we decided like this, this is the state machine for a job advert. 00:11:08.726 --> 00:11:12.606 align:middle So we started draft and then we can send it to review. 00:11:13.096 --> 00:11:15.466 align:middle While in review, we can trash it, untrash it, 00:11:15.466 --> 00:11:17.536 align:middle and we can send it to review again if you'd like. 00:11:17.536 --> 00:11:19.266 align:middle And from review you can publish and archive it. 00:11:19.806 --> 00:11:25.796 align:middle It is impossible to archive something that is in review or that is something that's in trash. 00:11:26.216 --> 00:11:27.006 align:middle It's impossible. 00:11:30.096 --> 00:11:30.626 align:middle Excellent. 00:11:31.316 --> 00:11:35.026 align:middle Since you are very confident now, what is this a workflow of? 00:11:40.796 --> 00:11:46.386 align:middle Someone said a pull request issue. 00:11:46.686 --> 00:11:47.746 align:middle Uh, I will say yes. 00:11:47.886 --> 00:11:51.646 align:middle Correct. So basically you start coding your pull request, 00:11:52.066 --> 00:11:54.476 align:middle you submit it to Travis, Travis runs for awhile. 00:11:54.656 --> 00:11:58.166 align:middle You may want to decide when you're waiting for review 00:11:58.166 --> 00:12:00.216 align:middle and then you may want to decide to update it. 00:12:00.216 --> 00:12:01.776 align:middle So we'll go back to Travis running. 00:12:02.246 --> 00:12:04.476 align:middle And maybe someone says, hey, we need some changes. 00:12:04.796 --> 00:12:08.116 align:middle So you go back to coding, then you update it, then send it to review 00:12:08.116 --> 00:12:13.486 align:middle and hopefully it gets merged or else it could be rejected and re-opened again. 00:12:14.766 --> 00:12:16.056 align:middle Seem straightforward? 00:12:16.806 --> 00:12:17.726 align:middle So how about this? 00:12:18.086 --> 00:12:19.626 align:middle Oh yeah, pull request. 00:12:19.626 --> 00:12:20.246 align:middle So how about this? 00:12:20.566 --> 00:12:24.306 align:middle What is it the workflow of? 00:12:27.056 --> 00:12:28.826 align:middle What is the state machine of? 00:12:34.496 --> 00:12:37.966 align:middle People usually yell out like, like you, sorry, like you did. 00:12:38.136 --> 00:12:38.786 align:middle You said doors. 00:12:38.886 --> 00:12:41.126 align:middle I'm like no, no, not doors, it's elevator doors. 00:12:41.316 --> 00:12:42.976 align:middle But you're equally correct. 00:12:43.056 --> 00:12:43.656 align:middle It's doors. 00:12:44.156 --> 00:12:46.806 align:middle So basically this is the four states that a set of doors can be in. 00:12:46.866 --> 00:12:51.446 align:middle Either the doors can be opened and then you press the close button and then be closing. 00:12:51.866 --> 00:12:54.996 align:middle While the closing we can press open button so they go to opening. 00:12:55.356 --> 00:12:59.826 align:middle It's impossible for doors to be open and then in one, the next instance be closed. 00:12:59.876 --> 00:13:01.536 align:middle They have to be closing, right? 00:13:02.816 --> 00:13:07.386 align:middle I think. I think we kind of know, know state machines now. 00:13:08.446 --> 00:13:10.076 align:middle Maybe business a dictates that... 00:13:10.406 --> 00:13:14.616 align:middle Maybe business a business dictates that you should have a form like this, 00:13:15.116 --> 00:13:16.566 align:middle like maybe a sign up form or whatever. 00:13:16.906 --> 00:13:21.176 align:middle So you can have a state machine to know where the user is in the form. 00:13:21.326 --> 00:13:26.266 align:middle So if you leave this process, you can, you can get back to where where he or she left off. 00:13:27.036 --> 00:13:31.376 align:middle And if your extra nice you can have back buttons so we can travel back and forth in this process. 00:13:32.036 --> 00:13:37.506 align:middle If you want to implement this, there's basically two implementations. 00:13:38.716 --> 00:13:40.626 align:middle I'm gonna can talk to them with them bot. 00:13:40.706 --> 00:13:42.086 align:middle No, I'm not going to talk with them. 00:13:42.086 --> 00:13:44.986 align:middle I'm gonna talk with you about the both of them - the implementations. 00:13:45.716 --> 00:13:50.256 align:middle The first implementation is the state pattern and that's using the Moore state machine. 00:13:51.136 --> 00:13:54.636 align:middle And a Moore state machine only cares about the current state. 00:13:55.476 --> 00:14:00.546 align:middle The next state only cares about, the next state is defined by the current state. 00:14:01.196 --> 00:14:05.186 align:middle The other state machine is the Mealy state machine and the next state depends 00:14:05.186 --> 00:14:06.996 align:middle on the current state and some input. 00:14:06.996 --> 00:14:12.466 align:middle I just want to say this out loud now and then I'm gonna repeat it later. 00:14:12.746 --> 00:14:15.246 align:middle Let's start with the state pattern and the Moore state machine. 00:14:16.686 --> 00:14:20.986 align:middle This is basically what you easily read on wikipedia. 00:14:20.986 --> 00:14:22.276 align:middle You... a state. 00:14:22.276 --> 00:14:24.006 align:middle I'll click this. 00:14:24.536 --> 00:14:28.006 align:middle Say you want to implement, something like this. 00:14:28.006 --> 00:14:29.616 align:middle We want to implement a... 00:14:29.686 --> 00:14:33.876 align:middle something that reminds you to complete your profile, say a user signs up and you want to say 00:14:33.876 --> 00:14:37.286 align:middle like "Hey, you should add your name" and we remind them twice about adding their name. 00:14:37.656 --> 00:14:39.496 align:middle If in order to add your name, like we should, 00:14:39.496 --> 00:14:42.306 align:middle hey you should update your image or you should add your resume. 00:14:43.276 --> 00:14:50.676 align:middle So implementing this with a state pattern means that each of these five states have a class 00:14:51.196 --> 00:14:53.546 align:middle and that class itself only have one f unction. 00:14:53.866 --> 00:14:54.856 align:middle It has a Send function. 00:14:55.566 --> 00:15:02.146 align:middle And, and that calls itself decides what to do and where to go next. 00:15:03.596 --> 00:15:04.026 align:middle Makes sense? 00:15:04.856 --> 00:15:10.196 align:middle So the idea here is that we have, have, we have a worker like a cron job saying like: Hey, 00:15:10.196 --> 00:15:13.226 align:middle give me all the state machine from database somehow and start yourself. 00:15:13.546 --> 00:15:18.086 align:middle I don't really care what you're doing - you just send the email, send the correct emails. 00:15:20.656 --> 00:15:28.146 align:middle So in the implementing this, I'm basically looping over all the states and if the, 00:15:28.356 --> 00:15:30.736 align:middle if the state machine says "I'm done", then we're done. 00:15:31.136 --> 00:15:34.586 align:middle So any given state just looks something like this. 00:15:34.656 --> 00:15:40.066 align:middle I, this is, I mean, you send an email and then I say go to next state. 00:15:41.616 --> 00:15:42.046 align:middle Makes sense? 00:15:42.736 --> 00:15:46.236 align:middle We should obviously do a little, we should modify this a little bit. 00:15:46.276 --> 00:15:49.546 align:middle We can maybe say like, if the user doesn't have a name, 00:15:50.026 --> 00:15:53.186 align:middle if the user do have a name, go to add your image state. 00:15:53.876 --> 00:15:56.926 align:middle So the state itself says where to go next. 00:15:57.226 --> 00:16:00.216 align:middle The sates itself decides everything what to do. 00:16:00.776 --> 00:16:03.846 align:middle And the state is a single class. 00:16:08.346 --> 00:16:11.036 align:middle We should also be a little bit more friendly. 00:16:11.386 --> 00:16:16.286 align:middle This would actually flood the user's email address, so uh, email inbox. 00:16:16.346 --> 00:16:21.626 align:middle So we should: you should be in this state for at least seven days until we send another email. 00:16:24.726 --> 00:16:27.516 align:middle I know this might feel weird. 00:16:28.266 --> 00:16:30.746 align:middle I know this might feel like that's not really PHP. 00:16:31.576 --> 00:16:34.066 align:middle It feels more like Java or something else. 00:16:34.416 --> 00:16:36.656 align:middle It feels weird and I will agree with you. 00:16:38.036 --> 00:16:38.946 align:middle This feels a bit weird. 00:16:40.036 --> 00:16:43.516 align:middle Using this and, for the simple state machine I showed you the five states, 00:16:43.596 --> 00:16:45.366 align:middle you have a bunch of classes like this. 00:16:45.766 --> 00:16:47.516 align:middle And they all pretty much look the same. 00:16:47.856 --> 00:16:51.446 align:middle Each of this state just look, oh, they look like this. 00:16:52.956 --> 00:17:01.906 align:middle So I... with this I would like you to get an idea how the state pattern works and some 00:17:01.906 --> 00:17:03.336 align:middle of you guys are nodding politely. 00:17:03.456 --> 00:17:04.076 align:middle Excellent. 00:17:05.156 --> 00:17:06.486 align:middle You obviously have issues with this. 00:17:06.486 --> 00:17:09.906 align:middle I mean you have issues: how do you store the state machines in this database? 00:17:10.246 --> 00:17:11.536 align:middle How do you keep track of the state? 00:17:11.716 --> 00:17:13.696 align:middle How do you store the createdAt entity... 00:17:14.186 --> 00:17:20.946 align:middle or data. Also it feels kind of weird that you have one class with state. 00:17:21.636 --> 00:17:24.596 align:middle So let's, let's do something different. 00:17:25.096 --> 00:17:29.016 align:middle Like now we know the Moore state machine, we know the state pattern, 00:17:29.426 --> 00:17:30.926 align:middle so let's look at something different. 00:17:30.996 --> 00:17:34.096 align:middle Let's look at something that feels more like PHP. 00:17:34.096 --> 00:17:40.236 align:middle And I'm going to stress this multiple times: the Mealy state machine, the next state depends 00:17:40.236 --> 00:17:42.866 align:middle on the current state and some input. 00:17:44.236 --> 00:17:47.636 align:middle So it's obviously a little bit more flexible. 00:17:48.236 --> 00:17:49.936 align:middle Let's try. 00:17:49.936 --> 00:17:54.006 align:middle Let's consider this state machine again, you all know this by heart now. 00:17:54.306 --> 00:17:55.786 align:middle If you would write an implementation of this, 00:17:55.896 --> 00:18:02.246 align:middle if we like PHP developers would write an implementation of this, how would we do? 00:18:02.496 --> 00:18:03.376 align:middle Well, what's the first? 00:18:03.376 --> 00:18:04.686 align:middle We obviously need a class, right? 00:18:04.736 --> 00:18:07.236 align:middle We need a state machine - traffic light state machine class. 00:18:08.036 --> 00:18:12.376 align:middle And we kind of want to have a function that applies new state. 00:18:13.856 --> 00:18:19.366 align:middle And I imagine it to be good to have like a function that "can I apply this state?" 00:18:24.936 --> 00:18:27.286 align:middle Good. So let's. 00:18:27.876 --> 00:18:30.106 align:middle So I create my state machine looking something like this. 00:18:30.706 --> 00:18:37.966 align:middle I define all my states as constants and I also choose to have a private property called state. 00:18:38.946 --> 00:18:45.456 align:middle And then I just, via a switch statement say: if someone say: "Can I do transition to yellow?" 00:18:45.886 --> 00:18:50.266 align:middle I check if I'm currently in state green and someone says "can (I go) to yellow?" 00:18:50.566 --> 00:18:52.066 align:middle Then sure, that's allowed. 00:18:52.816 --> 00:18:58.036 align:middle If I'm in state red and someone says "to green", then it's obviously no, I return false. 00:19:02.806 --> 00:19:04.846 align:middle And I do a similar, very similar thing for apply. 00:19:04.846 --> 00:19:14.716 align:middle I just do something like this. 00:19:14.906 --> 00:19:16.136 align:middle So would this state machine. 00:19:16.726 --> 00:19:20.226 align:middle I can easily, I can easily implement my... 00:19:20.226 --> 00:19:23.926 align:middle This, this class is easily implement my traffic light state machine, right? 00:19:27.746 --> 00:19:31.566 align:middle There's an issue though: this state machine has a private state. 00:19:32.246 --> 00:19:34.676 align:middle So I need to store the state machine in the database somehow. 00:19:36.126 --> 00:19:38.176 align:middle This state machine is only for one traffic light. 00:19:38.666 --> 00:19:41.376 align:middle If I have multiple traffic lights in my system, I have to have multiple state machines 00:19:41.376 --> 00:19:44.526 align:middle which each needs to be stored in the database, because of the state property. 00:19:45.276 --> 00:19:48.186 align:middle What if I made my state machines more stateless? 00:19:48.886 --> 00:19:54.736 align:middle Like I removed the private state and put that on the, on the traffic light entity? 00:19:55.226 --> 00:19:56.176 align:middle So I did something like this. 00:19:56.656 --> 00:20:02.226 align:middle Can this specific traffic light do this transition? 00:20:02.226 --> 00:20:05.266 align:middle So now I don't need to store the state machine in the database anymore. 00:20:05.406 --> 00:20:08.646 align:middle I can use this state machine for all the traffic lights. 00:20:10.086 --> 00:20:13.196 align:middle It feels quite, feels quite good, right? 00:20:13.476 --> 00:20:14.436 align:middle Yes. It feels quite good. 00:20:15.706 --> 00:20:17.176 align:middle I diddothe same thing with apply function. 00:20:17.316 --> 00:20:21.246 align:middle I just say $trafficLight->getCurrentState() and I have a $trafficLight->setState(). 00:20:22.866 --> 00:20:24.626 align:middle Very similar, very small changes. 00:20:24.996 --> 00:20:29.216 align:middle And I feel pretty good about the state machine at this point and whenever I'm using this, 00:20:29.456 --> 00:20:35.906 align:middle it might be an idea of mine to have a function that allows more traffic. 00:20:37.246 --> 00:20:42.696 align:middle I mean if, if, if the state is currently in the red state and I want to allow more traffic, 00:20:43.086 --> 00:20:47.086 align:middle I just, whatever state they're currently in, I just move it towards green. 00:20:47.346 --> 00:20:49.446 align:middle So I might attempt to do something like this. 00:20:51.016 --> 00:20:53.746 align:middle So I know if I call allow more traffic twice. 00:20:53.746 --> 00:21:01.706 align:middle I will definitely be in green. 00:21:01.896 --> 00:21:03.486 align:middle You look confused and you should. 00:21:03.966 --> 00:21:06.396 align:middle Because this was like my trickery, but I didn't trick you. 00:21:06.866 --> 00:21:09.646 align:middle If I want to make this state machine more generic, more reusable, 00:21:09.646 --> 00:21:11.356 align:middle obviously this is a horrible idea. 00:21:12.396 --> 00:21:18.546 align:middle Right? So if I'm going to make it more reusable, I may want to consider instead 00:21:18.546 --> 00:21:22.086 align:middle of having the states all over the place, I may want to put them 00:21:22.086 --> 00:21:24.556 align:middle in a, uh, in a property like this. 00:21:26.056 --> 00:21:32.636 align:middle So with this weird array looking thing, it's actually me trying to be a bit clever again. 00:21:33.066 --> 00:21:35.776 align:middle So I can just say: can I do the transition? 00:21:36.096 --> 00:21:43.566 align:middle I was checking if this is, if this property is set, if this array key exists. 00:21:45.456 --> 00:21:48.146 align:middle I do the same kind of wizardry in apply. 00:21:48.916 --> 00:21:55.266 align:middle Do you feel confident with this? 00:21:55.476 --> 00:21:58.536 align:middle You kind of understand it at least that's, that's the most important thing. 00:21:59.576 --> 00:22:01.756 align:middle However, say you want to make this even more generic. 00:22:02.286 --> 00:22:04.396 align:middle I mean, I shouldn't, I mean this is only for traffic lights. 00:22:04.696 --> 00:22:05.626 align:middle I said, traffic light here. 00:22:05.626 --> 00:22:07.046 align:middle What if I do something different? 00:22:07.286 --> 00:22:07.676 align:middle What if I... 00:22:09.376 --> 00:22:10.086 align:middle Oh, sorry. 00:22:11.656 --> 00:22:13.636 align:middle Oh, look, the states, it should be states here. 00:22:13.636 --> 00:22:19.746 align:middle What if I inject the states instead in a constructor like this? 00:22:20.146 --> 00:22:22.986 align:middle Then I have those states - I can do this for any kind 00:22:23.146 --> 00:22:24.776 align:middle of state machine and any kind of traffic light. 00:22:24.916 --> 00:22:27.236 align:middle And now, oh no, I have traffic lights over here. 00:22:27.426 --> 00:22:30.496 align:middle What if I did something like this to have the StateAwareInterface instead? 00:22:31.696 --> 00:22:35.866 align:middle And this StateAwareInterface just have a getCurrentState() and setState() method. 00:22:37.006 --> 00:22:39.776 align:middle With this class of 15 lines. 00:22:40.246 --> 00:22:43.966 align:middle This is actually a pretty good, pretty generic state machine, right? 00:22:44.886 --> 00:22:48.796 align:middle And it all feels (like) PHP, all in one class and I can configure it however 00:22:48.796 --> 00:22:50.876 align:middle like and use an object that I like. 00:22:51.526 --> 00:22:54.466 align:middle I hope we feel like we understand this. 00:22:56.076 --> 00:22:56.816 align:middle Does anyone have... 00:22:56.866 --> 00:22:58.786 align:middle oh no, I can't ask you for issues. 00:22:58.786 --> 00:23:01.726 align:middle Does everyone feel like you understand this class? 00:23:02.776 --> 00:23:03.356 align:middle Excellent. 00:23:03.526 --> 00:23:04.036 align:middle Excellent. 00:23:04.926 --> 00:23:07.886 align:middle I'll tell you a little bit of a secret. 00:23:07.886 --> 00:23:11.526 align:middle This is actually how the Workflow component works. 00:23:12.756 --> 00:23:14.816 align:middle This is the workflow of the Workflow component. 00:23:15.776 --> 00:23:23.166 align:middle And it was very true like two or three years ago, this was exactly the Workflow component. 00:23:23.706 --> 00:23:30.696 align:middle And nowadays there's a lot of edge cases, but in principle it works exactly like this. 00:23:31.296 --> 00:23:34.766 align:middle The Workflow component all have some more functions we showed. 00:23:34.766 --> 00:23:37.636 align:middle I showed an implementation of "can we do the transition?" 00:23:37.636 --> 00:23:38.456 align:middle And "apply transition". 00:23:38.526 --> 00:23:43.736 align:middle The workflow component has two more methods saying "like what state are we currently in?" 00:23:43.736 --> 00:23:45.656 align:middle And what are my valid transitions? 00:23:46.276 --> 00:23:49.176 align:middle So let's show some examples. 00:23:49.926 --> 00:23:51.586 align:middle Same old job advert workflow again. 00:23:51.586 --> 00:23:56.046 align:middle In the Workflow component, this might look like something like this. 00:23:56.626 --> 00:24:02.876 align:middle The red circle is the current state, so I can say: give me the state machine for job adverts. 00:24:04.126 --> 00:24:09.196 align:middle And I say give me the current marking for this entity and give me the places. 00:24:10.516 --> 00:24:12.846 align:middle And marking here sounds weird. 00:24:12.846 --> 00:24:18.526 align:middle It's because it's basically the abstraction of getting properties from the, from the Advert. 00:24:19.966 --> 00:24:22.436 align:middle If you ignore that, it's, this is very simple, right? 00:24:23.536 --> 00:24:26.766 align:middle So I get an array back and I see I'm in Draft. 00:24:27.036 --> 00:24:31.496 align:middle I can continue showing examples saying: state machine, can I do publish? 00:24:32.426 --> 00:24:34.506 align:middle No, I can't, but can I do "to review"? 00:24:35.326 --> 00:24:36.226 align:middle Yes, that's true I can. 00:24:36.526 --> 00:24:37.546 align:middle So I continue. 00:24:37.546 --> 00:24:43.406 align:middle I go to review and when I execute this line, it actually moves the circle away 00:24:43.406 --> 00:24:48.736 align:middle and from here I can say go to trash, go to draft and go to review again. 00:24:49.406 --> 00:24:58.126 align:middle And in this state I can say which are my enabled translations, and I get an array back 00:24:58.256 --> 00:25:03.736 align:middle to say I can go to publish and trash. 00:25:03.886 --> 00:25:08.196 align:middle I just, you just understand everything in the Workflow component. 00:25:08.196 --> 00:25:12.736 align:middle The Workflow component itself got like 15 classes and this is the most complex one. 00:25:13.326 --> 00:25:16.246 align:middle And you understand it fully now, which I think is quite... 00:25:17.246 --> 00:25:21.236 align:middle not impressive that you understand it, but it's impressive how simple Symfony components are. 00:25:22.646 --> 00:25:25.716 align:middle Uh, this is also, since this is Symfony, this is also available in Twig. 00:25:26.436 --> 00:25:32.416 align:middle Imagine, imagine when you're editing an advert on Happyr, 00:25:32.666 --> 00:25:35.126 align:middle imagine it looks exactly like, like Wordpress. 00:25:35.126 --> 00:25:40.166 align:middle You have this big text box in the middle and then you have a sidebar with like trash, 00:25:40.166 --> 00:25:42.976 align:middle publish and stuff button like this. 00:25:43.636 --> 00:25:45.416 align:middle This is the code for the sidebar. 00:25:45.766 --> 00:25:51.016 align:middle So I'm checking if the workflow "can" go to review, then show the link for review. 00:25:51.806 --> 00:25:57.216 align:middle If the, the, the, this advert can be published, then show the link for published. 00:25:58.056 --> 00:26:04.426 align:middle So the same sidebar will look differently on different adverts. 00:26:04.976 --> 00:26:14.146 align:middle And if you are, if you're smart with the naming of your work for transitions and you're naming 00:26:14.146 --> 00:26:17.396 align:middle of the routes, you can do something like this to print the sidebar. 00:26:17.426 --> 00:26:23.426 align:middle I want to show this because it's, it's possible, but you probably shouldn't do this. 00:26:23.776 --> 00:26:27.136 align:middle I do want to say that... 00:26:27.376 --> 00:26:31.616 align:middle I mean, I think this is pretty cool, right? 00:26:32.546 --> 00:26:34.746 align:middle You, sorry. 00:26:35.486 --> 00:26:44.746 align:middle I need to reverse, blah blah, this is a sidebar, decisions... 00:26:45.906 --> 00:26:47.656 align:middle This is pretty cool, right? 00:26:47.656 --> 00:26:51.766 align:middle Your sidebar really, it changes depending on the states. 00:26:52.366 --> 00:26:58.576 align:middle And what's cool here though is on a business meeting, we sat down and someone asked, 00:26:58.576 --> 00:27:01.776 align:middle how come you can't trash something that's in draft? 00:27:02.476 --> 00:27:07.996 align:middle It's obviously no arrow here, but what's the reason? 00:27:09.156 --> 00:27:11.276 align:middle And I'm like, yeah, there is no real reason. 00:27:11.426 --> 00:27:14.736 align:middle So let's, add this arrow. 00:27:14.826 --> 00:27:18.046 align:middle And here's, here's the kicker. 00:27:18.476 --> 00:27:22.046 align:middle I only changed the whiteboard. 00:27:22.046 --> 00:27:26.216 align:middle I want to change how the, how the state machine looks like. 00:27:26.436 --> 00:27:28.256 align:middle I did not change any of my models. 00:27:28.766 --> 00:27:30.666 align:middle I did not change any of my controller. 00:27:31.086 --> 00:27:33.806 align:middle I did not change any of my services, I did not change Twig layer, 00:27:33.806 --> 00:27:36.066 align:middle I didn't change anything but my configuration. 00:27:36.756 --> 00:27:47.116 align:middle And still with this change, I will see the trash in the sidebar when the advert is in draft. 00:27:47.366 --> 00:27:51.266 align:middle And that's pretty cool. 00:27:51.266 --> 00:27:56.726 align:middle A year ago, I did this presentation and when I said that's pretty cool. 00:27:56.916 --> 00:27:58.476 align:middle People like, yeah, that's cool. 00:27:58.476 --> 00:28:00.256 align:middle Good job, and they were kind of cheering. 00:28:00.946 --> 00:28:05.706 align:middle But you become the words, not only to be excited with me. 00:28:06.566 --> 00:28:10.516 align:middle So I want to change the configuration And the configuration looked like this. 00:28:11.026 --> 00:28:14.096 align:middle It's super simple, This is my, this is my core of my business. 00:28:14.096 --> 00:28:15.056 align:middle This is my business logic. 00:28:16.576 --> 00:28:22.846 align:middle If you're really, really paying attention, you might spot a weird thing here. 00:28:24.366 --> 00:28:27.406 align:middle I told you that a workflow can have, no sorry, 00:28:27.406 --> 00:28:29.766 align:middle I told you the the state machine only can have one input and one output. 00:28:29.996 --> 00:28:32.596 align:middle And clearly I have two inputs here. 00:28:33.766 --> 00:28:37.676 align:middle This Symfony configuration is smart enough to know like, oh, 00:28:37.966 --> 00:28:42.946 align:middle I can make two transition of this. 00:28:42.946 --> 00:28:47.106 align:middle So it, it says, it looks like only one, but it's actually gonna to become two transitions. 00:28:48.686 --> 00:28:52.206 align:middle And also quickly want to show you a multistep signup form. 00:28:52.916 --> 00:28:57.726 align:middle Business may dictate that this is the way we sign up to our service. 00:28:57.986 --> 00:29:00.906 align:middle So have an intro, you add your name, you add your email, 00:29:00.906 --> 00:29:02.336 align:middle you add your twitter, and then you're done. 00:29:03.376 --> 00:29:07.066 align:middle And doing this workflow in the configuration is simple, you just do it like this. 00:29:07.146 --> 00:29:11.116 align:middle You just say that this is a state machine, this is my places, 00:29:11.116 --> 00:29:12.526 align:middle and this is how you move between places. 00:29:13.556 --> 00:29:17.196 align:middle And business might say this is good and all, but we want to have back buttons. 00:29:17.196 --> 00:29:19.436 align:middle We want to have a workflow like this where you go back. 00:29:19.536 --> 00:29:21.706 align:middle And we said, sure, no worries. 00:29:22.256 --> 00:29:23.756 align:middle We just do something like this. 00:29:24.126 --> 00:29:26.196 align:middle However, this is not valid YAML, right? 00:29:27.256 --> 00:29:30.386 align:middle You cannot have multiple keys on the same level which is called back. 00:29:31.206 --> 00:29:34.836 align:middle So what we need to do, we need to do something like this instead. 00:29:35.256 --> 00:29:40.026 align:middle We add arbitrary numbers or arbitrary names and then we have the name. 00:29:40.806 --> 00:29:42.776 align:middle So this how we get around the issue with YAML. 00:29:43.196 --> 00:29:45.816 align:middle So with this you can actually please the business to have back buttons. 00:29:46.156 --> 00:29:52.286 align:middle And I know I've been talking a lot about state machines now and I haven't really... 00:29:52.286 --> 00:29:55.016 align:middle This is called the Workflow component. 00:29:55.166 --> 00:29:57.826 align:middle And it says workflow like all over the place here, right? 00:29:58.276 --> 00:30:01.286 align:middle So what is the difference between a state machine and workflow? 00:30:01.286 --> 00:30:04.626 align:middle In the beginning I mentioned the state machine is a reduced workflow, 00:30:04.626 --> 00:30:06.596 align:middle but what is the actual, what is the actual difference? 00:30:06.796 --> 00:30:12.016 align:middle As an example, I want to show you this: this an example of a workflow. 00:30:12.296 --> 00:30:13.676 align:middle Previously we've only seen state machines. 00:30:13.816 --> 00:30:15.386 align:middle This is the example of a workflow. 00:30:15.866 --> 00:30:20.086 align:middle And the main difference in a workflow and a state machine is that in a workflow, 00:30:20.286 --> 00:30:22.286 align:middle you may be in two places at once. 00:30:23.826 --> 00:30:27.676 align:middle It might feel weird, but it's actually valid. 00:30:27.676 --> 00:30:30.096 align:middle A workflow more or less describes a process. 00:30:30.606 --> 00:30:34.476 align:middle A state machine describes traffic lights, when you actually go back 00:30:34.596 --> 00:30:36.246 align:middle to the beginning and stuff - how you move. 00:30:36.506 --> 00:30:43.456 align:middle So this is a workflow for a blog post: it's first a draft, then you request reviews 00:30:43.966 --> 00:30:48.666 align:middle and then you get in, you get in the places for waiting for spellchecker and waiting 00:30:48.666 --> 00:30:49.846 align:middle for the journalist at the same time. 00:30:49.846 --> 00:30:54.406 align:middle So there's an example where a transition that makes you to be in two places at once. 00:30:54.966 --> 00:30:56.756 align:middle And spellchecker is probably automatic, right? 00:30:57.026 --> 00:30:59.836 align:middle So that's pretty quick, but you have to wait for the journalist. 00:31:00.526 --> 00:31:05.376 align:middle And it might be tempting to try to publish this blog post right now. 00:31:05.376 --> 00:31:11.286 align:middle But you can't execute the publishe transition because both its inputs are not fulfilled: 00:31:11.286 --> 00:31:13.006 align:middle we don't have one of the inputs, right? 00:31:13.006 --> 00:31:20.346 align:middle So we have to wait for the journalists to catch up and then you can eventually publish it. 00:31:20.726 --> 00:31:26.036 align:middle I will also say a workflow rarely contains loops. 00:31:26.376 --> 00:31:29.286 align:middle It's rare that you go back in your workflow. 00:31:29.976 --> 00:31:32.536 align:middle However, state machines, loops are encouraged... 00:31:33.336 --> 00:31:39.006 align:middle kind of. People used to ask me: when should I use workflow when I use state machine? 00:31:39.426 --> 00:31:41.786 align:middle And the answer is boring. 00:31:41.786 --> 00:31:43.276 align:middle It's obviously: it depends. 00:31:44.476 --> 00:31:50.606 align:middle I tend to use workflow when there's a clear process. 00:31:51.236 --> 00:31:53.826 align:middle I use state machine for everything else. 00:31:53.946 --> 00:31:55.546 align:middle It's just how I like it. 00:31:56.116 --> 00:31:58.826 align:middle The most important thing is that you know which one you're using. 00:31:59.176 --> 00:32:00.676 align:middle You need to know how to relate to them. 00:32:01.356 --> 00:32:05.446 align:middle It's like, for 99 percent of the problems, it doesn't really matter which one you're using. 00:32:06.046 --> 00:32:07.996 align:middle But you should know which one you're using. 00:32:08.406 --> 00:32:12.076 align:middle Does it make sense? 00:32:12.116 --> 00:32:12.556 align:middle Excellent. 00:32:12.556 --> 00:32:12.936 align:middle Excellent. 00:32:13.326 --> 00:32:14.466 align:middle So back to the Workflow component. 00:32:16.006 --> 00:32:20.636 align:middle If you have been around in the Symfony community for awhile, you might notice Symfony have 00:32:20.636 --> 00:32:24.786 align:middle like 30 components and the components are very decoupled from each other, 00:32:25.076 --> 00:32:27.186 align:middle but they play really, really well with each other. 00:32:27.836 --> 00:32:29.556 align:middle And the secret there is events. 00:32:30.586 --> 00:32:33.936 align:middle Events is the thing that makes them play well with each other. 00:32:34.476 --> 00:32:36.686 align:middle And the workflow component is no exception. 00:32:36.996 --> 00:32:39.946 align:middle We have events or, the Workflow component has events for everything. 00:32:40.566 --> 00:32:45.656 align:middle We, all the events looks like this: you have a generic event, say workflow.leave. 00:32:45.966 --> 00:32:50.646 align:middle Then you have an event, say workflow - the job advert - when they leave. 00:32:51.116 --> 00:32:56.066 align:middle And you have events for, workflow, job_advert, leave, draft node. 00:32:57.436 --> 00:33:00.936 align:middle And all these, you have all these three types of events for everything. 00:33:01.986 --> 00:33:04.176 align:middle So we have workflow leave, when you're leaving a node. 00:33:04.176 --> 00:33:07.726 align:middle You have transition that would actually transition from one node to another. 00:33:08.066 --> 00:33:11.366 align:middle And when you enter the node, when you have been entered the node, 00:33:11.526 --> 00:33:12.826 align:middle and when a transition is completed. 00:33:13.336 --> 00:33:15.536 align:middle And then you have announce saying: Hey, I'm all done. 00:33:16.096 --> 00:33:18.526 align:middle It might feel weird that we have so many events. 00:33:18.526 --> 00:33:23.346 align:middle I mean these add up to like 21 events for each transition, which is a lot of events. 00:33:24.896 --> 00:33:26.576 align:middle However, there, there's a reason for all of them. 00:33:26.576 --> 00:33:30.616 align:middle Like, I know I've reviewed all the pull requests adding more events and they all makes sense 00:33:30.616 --> 00:33:32.466 align:middle in this specific weird edge case. 00:33:33.036 --> 00:33:35.736 align:middle You should only care about the one you care about. 00:33:35.736 --> 00:33:36.806 align:middle I mean, you shouldn't... 00:33:36.946 --> 00:33:38.766 align:middle I only use like leave and enter... 00:33:38.766 --> 00:33:39.646 align:middle and that's fine. 00:33:39.986 --> 00:33:41.586 align:middle So there's plenty of events. 00:33:41.726 --> 00:33:43.756 align:middle There's also this even more events. 00:33:43.756 --> 00:33:48.796 align:middle There's one event called the Guard event and the Guard event is something that you use for, 00:33:49.546 --> 00:33:52.986 align:middle adding extra logic, like external dependencies. 00:33:53.716 --> 00:33:56.256 align:middle So: can I publish this blog post? 00:33:56.656 --> 00:33:58.706 align:middle Like say we want to, we want to have a rule saying: 00:33:58.706 --> 00:34:03.936 align:middle you can only publish this blog post if it's between3 and 4 PM. 00:34:04.206 --> 00:34:07.096 align:middle Or if the database is online or if the manager is in the office 00:34:07.096 --> 00:34:09.526 align:middle or if you have the role ROLE_PUBLISHER. 00:34:10.286 --> 00:34:16.536 align:middle So a Guard, a Guard event is how you add this extra knowledge to your state machine. 00:34:16.536 --> 00:34:20.886 align:middle And I think you all are comfortable with events subscribers. 00:34:21.136 --> 00:34:24.976 align:middle I basically say at the bottom, I say: this is the event I'm listening to - 00:34:24.976 --> 00:34:28.806 align:middle workflow.job_advert.guard.publish - like the "got published" transition. 00:34:29.086 --> 00:34:32.416 align:middle Whenever that event is dispatch called the guardPublish() function 00:34:32.676 --> 00:34:34.646 align:middle and run this three lines in the middle. 00:34:35.226 --> 00:34:38.606 align:middle I would, I will assume that you are comfortable with this. 00:34:38.866 --> 00:34:44.516 align:middle Except for the Guard event, we may, we can register normal event listeners. 00:34:44.516 --> 00:34:48.776 align:middle Say you want to log every time you move from one node to another. 00:34:49.216 --> 00:34:53.156 align:middle So I say, the workflow, when the job advert leaves any node - 00:34:54.196 --> 00:34:56.796 align:middle workflow.job_advert.leave - then I just to do a logging. 00:34:57.116 --> 00:35:02.036 align:middle I say advert with ID performed transition from one node to another. 00:35:02.816 --> 00:35:05.266 align:middle It might be useful to have this kind of log message. 00:35:08.856 --> 00:35:09.986 align:middle I'm checking - you're still with me? 00:35:10.216 --> 00:35:11.846 align:middle It looks like most of you are with me. 00:35:12.376 --> 00:35:17.686 align:middle I... no surprise: I love the Workflow Component. 00:35:18.156 --> 00:35:20.026 align:middle I use the Workflow component all over the place. 00:35:20.366 --> 00:35:21.386 align:middle If I have... 00:35:21.526 --> 00:35:26.536 align:middle the Symfony Security components have the concept of voters, which are basically: 00:35:26.816 --> 00:35:31.516 align:middle if someone wants to watch, view an advert, I got to make sure that advert is published. 00:35:31.886 --> 00:35:35.406 align:middle And I'm using the Workflow component to make sure I am in state published. 00:35:36.206 --> 00:35:41.496 align:middle So here's a simple security voter and I say: if someone tries to view then I check this: 00:35:41.586 --> 00:35:46.516 align:middle if the state machine got the marking for the advert and marking is published, 00:35:46.516 --> 00:35:49.356 align:middle like if I'm in published state, then you're allowed to view it. 00:35:50.036 --> 00:35:52.016 align:middle You should not be allowed to view something that's in draft. 00:35:53.306 --> 00:35:56.486 align:middle So I used my state machine all over the place. 00:35:57.506 --> 00:36:00.786 align:middle I also use the state machine for domain events. 00:36:01.756 --> 00:36:08.406 align:middle I know for sure that no advert in my application will ever be published unless the 00:36:08.576 --> 00:36:11.976 align:middle workflow.job_advert.enter.published event is dispatched. 00:36:12.786 --> 00:36:14.536 align:middle I can trust that for sure. 00:36:15.006 --> 00:36:18.056 align:middle That's why I use this event for my domain knowledge. 00:36:18.056 --> 00:36:22.206 align:middle Like say business say: you should email all your users whenever an advert is published. 00:36:22.506 --> 00:36:24.506 align:middle And this is a good, is a good place to hook into this. 00:36:25.466 --> 00:36:28.406 align:middle So I never dispatch any events on my own, I just use the workflow events. 00:36:28.966 --> 00:36:33.776 align:middle Obviously we don't email all our users when adverts are published, I just wanted to say, 00:36:33.996 --> 00:36:36.576 align:middle but it's, an example how you use your domain logic with these events? 00:36:38.086 --> 00:36:46.386 align:middle Um, whenever, whenever I'm in business meetings and we, the business people say we need this 00:36:46.386 --> 00:36:50.006 align:middle and we need that and we gotta figure out a new way to do stuff. 00:36:50.096 --> 00:36:53.646 align:middle We write the workflow on the whiteboard. 00:36:54.296 --> 00:36:57.186 align:middle And we change our minds, we go back and we add new states. 00:36:57.456 --> 00:37:02.496 align:middle We, because business people, they tend to like graphs and images, they tend to like, 00:37:03.326 --> 00:37:05.686 align:middle big circles and squares and arrows between them. 00:37:06.006 --> 00:37:08.216 align:middle So it's easy to work with, work with a whiteboard. 00:37:09.556 --> 00:37:15.616 align:middle However, when the whiteboard meeting is done, I want to make sure, I go back to coding and I got 00:37:15.616 --> 00:37:18.656 align:middle to make sure that I have configured this properly. 00:37:19.206 --> 00:37:26.506 align:middle So I add my configuration and then I run this command, the dump command and I'd get an image. 00:37:26.506 --> 00:37:31.066 align:middle I mean the dump command just prints out some text and I use this program called dots 00:37:31.196 --> 00:37:35.446 align:middle or this script called dot which converts, takes to an image, and I can get this image. 00:37:35.956 --> 00:37:39.556 align:middle So then I compare the whiteboard with my image and more often 00:37:39.556 --> 00:37:41.756 align:middle than not I made a mistake in my configuration. 00:37:42.176 --> 00:37:45.476 align:middle So this is a good way to make sure you configure this properly. 00:37:46.086 --> 00:37:49.926 align:middle And so I usually dump two or three times and then I, 00:37:50.246 --> 00:37:51.856 align:middle then I know I got the right conflagration. 00:37:53.276 --> 00:37:57.266 align:middle And I know I talked a lot, and state machines they sure are great. 00:37:57.266 --> 00:38:00.276 align:middle I gives us, I've told you so many benefits, but how do... 00:38:00.276 --> 00:38:03.806 align:middle I mean where... 00:38:04.096 --> 00:38:05.216 align:middle so I want to give you some hints. 00:38:05.216 --> 00:38:11.196 align:middle I want to give you some: if you ever have, if you ever have code like this, this is code, 00:38:11.196 --> 00:38:16.876 align:middle I've written, I wrote a cCRMm or whatever it's called, basically for salespeople 00:38:16.876 --> 00:38:21.386 align:middle and they have a quotation and I defined the Quotation can be 00:38:21.386 --> 00:38:23.296 align:middle in these three states, four states. 00:38:23.556 --> 00:38:26.686 align:middle I even have a property called status. 00:38:26.686 --> 00:38:31.016 align:middle And whatever you see code like this in your application, you should know like, hey, 00:38:31.216 --> 00:38:35.286 align:middle maybe I should use a state machine for this. 00:38:35.586 --> 00:38:40.306 align:middle Also, when you're looking at your database and you see something like this. 00:38:40.596 --> 00:38:44.716 align:middle Like have boolean for active, a boolean for ended, a boolean for closed. 00:38:45.236 --> 00:38:49.436 align:middle This is also a good sign, like "hey maybe a state machine will be better in this scenario" 00:38:50.566 --> 00:38:54.346 align:middle And people asking me: "Oh, Tobias, should you really have state machines 00:38:54.346 --> 00:38:56.426 align:middle if you only have three or four states?" 00:38:57.106 --> 00:38:59.226 align:middle And the answer is obviously it depends. 00:38:59.406 --> 00:39:01.636 align:middle Are you sure you never ever would add more states? 00:39:02.026 --> 00:39:04.096 align:middle How are the rules between those states? 00:39:04.096 --> 00:39:04.836 align:middle How do you move? 00:39:05.106 --> 00:39:09.226 align:middle And I would say, if you want to make sure you don't have any bugs. 00:39:09.526 --> 00:39:11.776 align:middle Yes, a state machine might be a good idea. 00:39:12.346 --> 00:39:17.576 align:middle Obviously if you're only have two states, I mean it all depends and I understand, 00:39:17.716 --> 00:39:20.256 align:middle I'm sure you're getting the gist. 00:39:20.256 --> 00:39:21.586 align:middle So how about processes? 00:39:22.676 --> 00:39:24.766 align:middle If you don't have a quotation, but a process. 00:39:25.196 --> 00:39:29.046 align:middle What if you're doing e-commerce, it's obviously a process here. 00:39:29.326 --> 00:39:34.156 align:middle You obviously create an order somehow and items are being added to that order 00:39:34.316 --> 00:39:38.406 align:middle and then you need the user to fill in the delivery address and then you need them 00:39:38.676 --> 00:39:43.876 align:middle to add the payment method and then you need to call or somehow notify the delivery team 00:39:43.996 --> 00:39:45.496 align:middle to make sure that that order is delivered. 00:39:46.566 --> 00:39:50.986 align:middle And this is also like if you have this strict workflow, 00:39:51.206 --> 00:39:52.816 align:middle you should think of the Workflow component. 00:39:52.816 --> 00:39:56.786 align:middle You should think: "Hey, maybe, maybe I should use a workflow here." 00:39:56.876 --> 00:40:00.806 align:middle And then you start drawing on the whiteboard: you draw the order is created, 00:40:01.146 --> 00:40:06.456 align:middle and then somehow we add an item we have transition add item, so the item is added. 00:40:06.986 --> 00:40:13.846 align:middle And then you add the shipping and then you go to the checkout and after the order is confirmed. 00:40:14.606 --> 00:40:15.646 align:middle And you look at this. 00:40:15.646 --> 00:40:16.706 align:middle Yeah, sure, this makes sense. 00:40:16.706 --> 00:40:17.736 align:middle This is a clear workflow. 00:40:18.006 --> 00:40:23.626 align:middle However, this means a user can only can add one item, right? 00:40:23.626 --> 00:40:27.296 align:middle So we need to add an extra arrow here. 00:40:27.656 --> 00:40:30.806 align:middle The user can add more than one item so it can buy more stuff from you, right? 00:40:32.276 --> 00:40:38.486 align:middle And this, it's pretty simple: you just go through the workflow and the item added, sure, 00:40:38.486 --> 00:40:43.016 align:middle add another item, add more items, add shipping, and then order confirmed. 00:40:43.196 --> 00:40:47.266 align:middle And the cool thing here is: this will, each of these steps will dispatch an event. 00:40:48.126 --> 00:40:52.476 align:middle And on this event I have an event listener because this is my domain logic. 00:40:52.846 --> 00:40:58.116 align:middle I can trust that this event listener is executed each time an order is confirmed. 00:40:58.436 --> 00:41:02.006 align:middle And I just asked the delivery service to take care of this order somehow. 00:41:02.996 --> 00:41:03.436 align:middle Makes Sense? 00:41:04.606 --> 00:41:11.166 align:middle So using the state machine, I also know that no order will ever be completed 00:41:11.166 --> 00:41:13.776 align:middle or confirmed unless I added the shipping address. 00:41:15.036 --> 00:41:18.376 align:middle It's literally impossible to complete an order without adding a shipping address. 00:41:19.586 --> 00:41:25.956 align:middle So what I basically want to say is, it all comes down to this: 00:41:26.176 --> 00:41:30.296 align:middle Using the Symfony Workflow component will make your write fewer bugs. 00:41:30.956 --> 00:41:38.776 align:middle And I hope this short presentation of mine have given you a new way of thinking, 00:41:38.776 --> 00:41:40.576 align:middle a new way to relate to your problems. 00:41:41.076 --> 00:41:42.726 align:middle Thank very much. 00:41:43.036 --> 00:41:53.746 align:middle Thank you. 00:41:54.026 --> 00:41:56.986 align:middle I will share my slides on joind.in. 00:41:57.456 --> 00:42:00.876 align:middle And so if you, if you're interested in anything, you please feel free. 00:42:01.246 --> 00:42:05.136 align:middle If you have any questions, I think we have a few minutes and I will throw this cube at you. 00:42:05.206 --> 00:42:08.516 align:middle Anyone want to have a cube? 00:42:12.356 --> 00:42:14.696 align:middle There's a question over there, please help me. 00:42:16.916 --> 00:42:18.236 align:middle Two rows back. 00:42:18.416 --> 00:42:19.856 align:middle Three rows back. 00:42:22.106 --> 00:42:27.376 align:middle Did you activate the cube? 00:42:29.636 --> 00:42:31.446 align:middle It was a mistake. 00:42:31.776 --> 00:42:33.406 align:middle Oh, okay, mistake question. 00:42:33.646 --> 00:42:45.086 align:middle Someone else - just throw it to someone waving over there. 00:42:45.366 --> 00:42:50.556 align:middle Whoever has the laser pointer in their eye. 00:42:50.556 --> 00:42:54.426 align:middle Sorry, can you hear me? 00:42:54.796 --> 00:42:55.236 align:middle Okay, great. 00:42:55.666 --> 00:42:59.036 align:middle So a question is really simple: where is e-commerce here? 00:42:59.156 --> 00:42:59.726 align:middle Where's the camera? 00:42:59.726 --> 00:43:02.676 align:middle I don't know where the camera is - oh there's the camera. 00:43:02.676 --> 00:43:06.676 align:middle I'm saying this was callex using the workflow component for E-commerce. 00:43:07.046 --> 00:43:10.126 align:middle Ah, where is the e-commerce? 00:43:10.396 --> 00:43:15.066 align:middle Yeah. I assume that you missed my five minutes beginning. 00:43:15.066 --> 00:43:16.586 align:middle Michelle sadly got sick. 00:43:16.876 --> 00:43:18.806 align:middle So I did a stand-in talk about Workflow component. 00:43:19.236 --> 00:43:24.286 align:middle So yes, I missed a lot of e-commerce stuff and we can only blame Michelle's three year old kid. 00:43:24.726 --> 00:43:34.036 align:middle There's one more question and then I'm gonna let you all go. 00:43:34.376 --> 00:43:38.216 align:middle You hear me? 00:43:38.286 --> 00:43:45.456 align:middle Yes I do. Uh, so my question is how to properly connect workflows with the security. 00:43:45.536 --> 00:43:49.486 align:middle So you have two ways: you can write a guard listener, uh, 00:43:49.486 --> 00:43:53.606 align:middle to prevent some transitions based on security. 00:43:53.706 --> 00:43:59.286 align:middle Or you can, as you showed, you can do a voter and there decide based 00:43:59.336 --> 00:44:01.806 align:middle on workflow whether you can do something or not. 00:44:01.876 --> 00:44:03.266 align:middle So what's the correct way? 00:44:03.776 --> 00:44:05.086 align:middle It depends what you're trying to do. 00:44:05.316 --> 00:44:11.186 align:middle I show the voters, which, I will try to explain, I used for handling my app security. 00:44:11.186 --> 00:44:13.666 align:middle I used the state machine as a substitute, as a help. 00:44:14.246 --> 00:44:18.456 align:middle If you're going to add security, saying like you want to make sure... 00:44:18.936 --> 00:44:24.046 align:middle if you want to make sure that you have the correct role for doing 00:44:24.046 --> 00:44:26.216 align:middle such as this action, use the Guard event. 00:44:26.726 --> 00:44:29.506 align:middle Okay. So you do something like this. 00:44:29.956 --> 00:44:31.706 align:middle So both ways are correct? 00:44:31.706 --> 00:44:34.106 align:middle Both are correct depending on what you're actually trying to solve. 00:44:34.106 --> 00:44:34.986 align:middle Okay. Thank you. 00:44:35.716 --> 00:44:38.066 align:middle I will be around for the rest of the conference 00:44:38.196 --> 00:44:40.396 align:middle and I also told you the best speakers in the front. 00:44:40.786 --> 00:44:44.296 align:middle I'm doing a second talk at the very, very end of the conference for some reason. 00:44:44.666 --> 00:44:51.106 align:middle So if you're interested in Symfony 4 internals, please come and visit me then. 00:44:51.106 --> 00:44:57.346 align:middle Please review, rate all the speakers on joind.in it's very helpful for all of us. 00:44:58.706 --> 00:45:02.486 align:middle Thank you very much.