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Add documentation for CallbackChoiceLoader #7219

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Mar 3, 2017
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Add documentation for CallbackChoiceLoader #7219

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e5e9a5d
Add documentation for CallbackChoiceLoader
sawmurai Dec 3, 2016
731617f
Clearify behaviour of CallbackChoiceLoader
sawmurai Dec 3, 2016
5838635
Make lines shorter to comply with 80-char limit
javiereguiluz Dec 5, 2016
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21 changes: 21 additions & 0 deletions reference/forms/types/choice.rst
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Expand Up @@ -184,6 +184,27 @@ The ``choice_loader`` can be used to only partially load the choices in cases wh
a fully-loaded list is not necessary. This is only needed in advanced cases and
would replace the ``choices`` option.

You can use an instance of :class:`Symfony\\Component\\Form\\ChoiceList\\Loader\\CallbackChoiceLoader`
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Missing a versionadded note

if you want to take advantage of lazy loading::

use Symfony\Component\Form\ChoiceList\Loader\CallbackChoiceLoader;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
// ...

$builder->add('constants', ChoiceType::class, array(
'choice_loader' => new CallbackChoiceLoader(function() {
return StaticClass::getConstants();
},
));

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We could precise that, the call won't happen if there is a redirection (i.e the view is not built), AND if there is no pre set data or submitted data. Because otherwise we'll need to transform the value to a model choice (or the opposite) and that implies loading choices too.

This will cause the call of ``StaticClass::getConstants()`` to not happen if the
request is redirected and if there is no pre set or submitted data. Otherwise
the choice options would need to be resolved thus triggering the callback.

.. versionadded:: 3.2
The ability to use an instance of :class:`Symfony\\Component\\Form\\ChoiceList\\Loader\\CallbackChoiceLoader`
was introduced in Symfony 3.2

.. include:: /reference/forms/types/options/choice_name.rst.inc

.. include:: /reference/forms/types/options/choice_translation_domain.rst.inc
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