Describe validation callables

Author: W0rma

validation/callables.rst

@@ -0,0 +1,46 @@
+.. index::
+    single: Validation; Callables
+
+How to Use Validation Constraints in Callable Validation (Validation Callables)
+===============================================================================
+
+Sometimes you need to reuse Symfony's constraints in places like the :doc:`Console Component </components/console>`,
+to validate the answer to a console question. ``Validation::createCallable()``
+can be used to create a callable based on the given constraints::
+
+    use Symfony\Component\Console\Style\SymfonyStyle;
+    use Symfony\Component\Validator\Constraints\NotNull;
+    use Symfony\Component\Validator\Validation;
+
+    $io = new SymfonyStyle($input, $output);
+    $validation = Validation::createCallable(new NotBlank());
+
+    $wsdl = $io->ask('Wsdl location URL', null, $validation);
+
+The argument of ``createCallable()`` is variadic, so you can pass any number of constraints::
+
+    // ...
+    use Symfony\Component\Validator\Constraints\Length;
+    use Symfony\Component\Validator\Constraints\Url;
+
+    $validation = Validation::createCallable(new Length(['max' => 255]), new Url());
+
+.. versionadded:: 5.1
+
+    ``Validation::createCallable()`` was introduced in Symfony 5.1.
+
+The callable throws a ``ValidationFailedException`` if the validation failed.
+Use ``createValidCallable()`` if you want to use the callable in places like
+:doc:`OptionsResolver Component </components/options_resolver>` where booleans are expected::
+
+    use Symfony\Component\OptionsResolver\OptionsResolver;
+    use Symfony\Component\Validator\Validation;
+
+    $resolver = new OptionsResolver();
+    $resolver->setAllowedValues('name', Validation::createValidCallable(
+        new Assert\Length(['min' => 10 ])
+    ));
+
+.. versionadded:: 5.3
+
+    ``Validation::createValidCallable()`` was introduced in Symfony 5.3.