.. include:: /Includes.rst.txt

.. _extbase_error_action:

Error Action
============

Extbase offers an out of the box handling for errors. Errors might occur during
mapping of incoming action arguments. E.g. an argument can not be mapped or
validation did not pass.

How it works
------------

.. rst-class:: bignums-xxl

#. Extbase will try to map all arguments within :php:`ActionController`. During
   this process arguments will also be validated.

#. If an error occurred, the class will call the :php:`$this->errorMethodName`
   instead of determined :php:`$this->actionMethodName`.

#. The default is to call :php:`errorAction()` which will:

   #. Clear cache in case :typoscript:`persistence.enableAutomaticCacheClearing` is
      activated and current scope is frontend.

   #. Add an error :ref:`Flash Message <t3coreapi:flash-messages>`
      by calling :php:`addErrorFlashMessage()`.
      Which in turn will call :php:`getErrorFlashMessage()` to retrieve the
      message to show.

   #. Forward back to referring request. If no referrer exists, a plain text
      message will be displayed, fetched from
      :php:`getFlattenedValidationErrorMessage()`.

Overloading Behaviour
---------------------

Each of the above steps can be adjusted by implementing custom methods or
replacing values within properties. All of the above is `protected` and therefore
can be replaced.

:php:`errorMethodName` property
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Replacing the default value `errorAction` will result in a different method to
be called in case of an error.

:php:`errorAction()` method
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Replacing the default implementation can be used to define custom error
handling. E.g. the requested format could be checked and a prepared JSON result
could be returned.

:php:`getErrorFlashMessage()` method
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Can be replaced in order to return :php:`false` to prevent generation of a flash
message. Can also return any other custom string which will be placed inside the
generated flash message.

:php:`getFlattenedValidationErrorMessage()` method
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Can be replaced in order to display some other error message if no referrer
exists.