With implementations of this interface, existing types can be amended.
The Csrf extension, for example, now contains a class FormTypeCsrfExtension
that adds CSRF capabilities to the "form" type.
To register new type extensions in the DIC, tag them with "form.type_extension"
and the name of the extended type as alias.
The extension classes are now the only constructor argument of the FormFactory class. They replace the existing "type loader" classes.
new FormFactory(array(
new CoreExtension($validator, $storage),
new CsrfExtension($csrfProvider),
new DoctrineOrmExtension($em),
));
Together with a few upcoming commits this mechanism will make
* extension of the form framework in bundles and
* usage of the forms outside of Symfony2
much easier.
