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> Symfony 5 > API Platform 2 Part 1: Serious RESTful APIs
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12.

Filtering & Searching

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We're doing awesome! We understand how to expose a class as an API resource, we can choose which operations we want, and have full control over the input and output fields, including some "fake" fields like textDescription. There's a lot more to know, but we're doing great!

So what else does every API need? I can think of a few things, like pagination and validation. We'll talk about both of those soon. But what about filtering? Your API client - which might just be your JavaScript code, isn't going to always want to fetch every single CheeseListing in the system. What if you need the ability to only see published listings? Or what if you have a search on the front-end and need to find by title? These are called "filters": ways to see a "subset" of a collection based on some criteria. And API Platform comes with a bunch of them built-in!

Filtering by Published/Unpublished

Let's start by making it possible to only return published cheese listings. Well, in a future tutorial, we're going to make it possible to automatically hide unpublished listings from the collection. But, for now, our cheese listing collection returns everything. So let's at least make it possible for an API client to ask for only the published ones.

At the top of CheeseListing, activate our first filter with @ApiFilter(). Then, choose the specific filter by its class name: BooleanFilter::class... because we're filtering on a boolean property. Finish by passing the properties={} option set to "isPublished".

145 lines | src/Entity/CheeseListing.php
// ... lines 1 - 11
/**
// ... lines 13 - 22
* @ApiFilter(BooleanFilter::class, properties={"isPublished"})
// ... line 24
*/
class CheeseListing
// ... lines 27 - 145

Cool! Let's see what this did! Refresh! Oh... what it did was break our app!

The filter class BooleanFilter does not implement FilterInterface.

It's not super clear, but that error means that we forgot a use statement. This BooleanFilter::class is referencing a specific class and we need a use statement for it. It's... kind of a strange way to use class names, which is why PhpStorm didn't autocomplete it for us.

No problem, at the top of your class, add use BooleanFilter. But... careful... most filters support Doctrine ORM and Doctrine with MongoDB. Make sure to choose the class for the ORM.

146 lines | src/Entity/CheeseListing.php
// ... lines 1 - 6
use ApiPlatform\Core\Bridge\Doctrine\Orm\Filter\BooleanFilter;
// ... lines 8 - 146

Ok, now move over and refresh again.

We're back to life! Click "Try it out". Hey! We have a little isPublished filter input box! If we leave that blank and execute... looks like 4 results.

Choose true for isPublished and try it again. We're down to two results! And check out how this works with the URL: it's still /api/cheeses, but with a gorgeous ?isPublished=true or ?isPublished=false. So just like that, our API users can filter a collection on a boolean field.

Oh! Also, down in the response, there's a new hydra:search property. OoooOOO. It's a bit techy, but this is explaining that you can now search using an isPublished query parameter. It also gives information about which property this relates to on the resource.

Text Searching: SearchFilter

How else can we filter? What about searching by text? On top of the class, add another filter: @ApiFilter(). This one is called SearchFilter::class and has the same properties option... but with a bit more config. Say title set to partial. There are also settings to match on an exact string, the start of a string, end of a string or on word_start.

Anyways, this time, I remember that we need to add the use statement manually. Say use SearchFilter and auto-complete the one for the ORM.

148 lines | src/Entity/CheeseListing.php
// ... lines 1 - 7
use ApiPlatform\Core\Bridge\Doctrine\Orm\Filter\SearchFilter;
// ... lines 9 - 13
/**
// ... lines 15 - 25
* @ApiFilter(SearchFilter::class, properties={"title": "partial"})
// ... line 27
*/
class CheeseListing
// ... lines 30 - 148

Oh, and before we check this out, I'll click to open SearchFilter. This lives in a directory called Filter and... if I double click it... hey! We can see a bunch of other ones: ExistsFilter, DateFilter, RangeFilter, OrderFilter and more. These are all documented - but you can also jump right in and see how they work.

Anyways, go refresh the docs, open the GET collection operation and click to try it. Now we have a title filter box. Try... um... cheese and... Execute.

Oh, magnificent! It adds ?title=cheese to the URL... and matched three of our four listings. The hydra:search property now contains a second entry advertising this new way to filter.

If we want to be able to search by another property, we can add that too: description set to partial.

This is easy to set up, but this type of database search is still pretty basic. Fortunately, while we won't cover it in this tutorial, if you need a truly robust search, API Platform can integrate with Elasticsearch: exposing your Elasticsearch data as readable API resources. That's pretty freaking cool!

Let's check out two more filters: a "range" filter, which will be super useful for our price property and another one that's... a bit special. Instead of filtering the number of results, it allows an API client to choose a subset of properties to return in the result. That's next.