symfony2 dynamic form validation with collection, depending on fields value

Question

symfony

For example, I have a Post document, which can be either a simple post with a collection of paragraphs or a link post. A post can be created as a link and later edited with original content (paragraphs that are a collection)
Post fields: title , is_external , external_url , paragraphs .
A paragraph consists of: title , description . Description is required.

How can I validate form values ​​with the following rules:
If is_external is checked, external_url cannot be empty, and paragraphsmay not be checked at all. Otherwise external_url must be empty, the paragraphs collection must contain at least one entry, all paragraphs must be validated.

How to do it right?

Answer 1

To validate everything in the callback yourself?
symfony.com/doc/current/reference/constraints/Callback.html
Or write custom verification?
symfony.com/doc/current/cookbook/validation/custom_constraint.html
Sorry if I didn't understand something.

Answer 2

One of the good approaches is to create your own validator, which will validate not a property, but an entire class. symfony.com/doc/current/cookbook/validation/custom_constraint.html The big plus here is that you can then define it as a service if necessary, and inject dependencies into it.
It is also possible to process this check on the FormEvents::SUBMIT event (On >= 2.1 < 2.3 FormEvents::BIND), and if there is an error, then add it yourself addError(new FormError(/**… **/));

Answer 3

Why do you need form validation? You must have final model validation.
And in my opinion it would be more correct to divide this into 2 entities, and merge these entities on the sample