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Changing Validation Messages

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Check out the web debug toolbar: it's highlighted with the number of validation errors, which is pretty cool. It's even cooler because we can see where those are coming from.

The default message for the NotBlank constraint is obviously

This value should not be blank

We can easily change this by passing a message option to the annotation. But wait a second: we're going to use NotBlank a lot. Is there a way to customize the default message across the whole system?

Yea! All of these strings are passed through Symfony's translator. And we can take advantage of that to customize this message, even in English.

Enabling the Translator

First, in case you don't already have it enabled, open up app/config/config.yml. Activate the translator service by uncommenting out the translator key under framework:

74 lines | app/config/config.yml
// ... lines 1 - 11
// ... line 13
translator: { fallbacks: ["%locale%"] }
// ... lines 15 - 74

Refresh this page and watch the web debug toolbar. Suddenly, there's an extra icon that's coming from the translator. It's reporting that there are ten missing messages. In other words, we are apparently already sending ten messages through the translator that are missing translation strings.

This is because every form field and all validation errors are automatically sent through the translator. Nothing looks weird, because those strings are already English, so it's not really a problem that they aren't translated.

Changing Validation Messages

But, if you want to customize this message, copy it. And, notice, the domain is validators: that's basically a translation "category", and it's important for what we do next.

We don't have any translation files yet, so create a new directory called translations in app/Resources. Inside, add a new file: validators.en.yml. This is validators because the message is being translated in that domain.

Inside, paste the string and set it to "Hi! Please enter something for this field.":

"This value should not be blank.": Hi! Please enter *something* for this field :)

And that's it! Go back and refresh! Oh no, it didn't work! Well, I kind of expected that. Find your terminal, open a new tab, and run:

./bin/console cache:clear

You almost never need to worry about clearing your cache while developing but very occasionally, you'll find a quirk in Symfony that needs this. Sometimes, when you add a new translation file, this happens.

Let's refresh again. There it is!

So yay validation! There's one more constraint I want you to see: Callback. This is your Swiss army knife: it allows you to write whatever custom validation logic you want inside a method. There, you can create different validation errors and map them to any field.