How to limit string length allowed in a ckeditor sitting atop Sonata

Question

I am working on a Symfony 3.3 application that uses Sonata.

I want to limit the length of a string that can be entered into a ckeditor instance.

I add the following in my admin class:

            ->add('caption', 'ckeditor', [
                'required'=>false,
                'label' => 'media.caption',
            ])

... and then I get stuck, not knowing how to proceed.

Is there a simple way to get the application to politely tell the user that his text needs to be shorter?

Answer 1

I ended up adding the following at the end of my admin class, per this page:

public function validate(ErrorElement $errorElement, $object)
{
    $errorElement
        ->with('caption')
        ->assertLength(['max' => 32])
        ->end()
    ;
}