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<sect1 id="zend.controller.dispatcher">
    <title>The Dispatcher</title>

    <sect2 id="zend.controller.dispatcher.overview">
        <title>Overview</title>

        <para>
            Dispatching is the process of taking the request object,
            <classname>Zend_Controller_Request_Abstract</classname>, extracting the module
            name, controller name, action name, and optional parameters
            contained in it, and then instantiating a controller and calling an
            action of that controller. If any of the module, controller, or
            action are not found, it will use default values for them.
            <classname>Zend_Controller_Dispatcher_Standard</classname> specifies
            <emphasis>index</emphasis> for each of the controller and action defaults
            and <emphasis>default</emphasis> for the module default value, but allows
            the developer to change the default values for each using the
            <methodname>setDefaultController()</methodname>,
            <methodname>setDefaultAction()</methodname>, and
            <methodname>setDefaultModule()</methodname> methods, respectively.
        </para>

        <note>
            <title>Default Module</title>

            <para>
                When creating modular applications, you may find that you want
                your default module namespaced as well (the default
                configuration is that the default module is
                <emphasis>not</emphasis> namespaced). As of 1.5.0, you can now
                do so by specifying the <property>prefixDefaultModule</property> as
                <constant>TRUE</constant> in either the front controller or your dispatcher:
            </para>

            <programlisting language="php"><![CDATA[
// In your front controller:
$front->setParam('prefixDefaultModule', true);

// In your dispatcher:
$dispatcher->setParam('prefixDefaultModule', true);
]]></programlisting>

            <para>
                This allows you to re-purpose an existing module to be the
                default module for an application.
            </para>
        </note>

        <para>
            Dispatching happens in a loop in the front controller. Before
            dispatching occurs, the front controller routes the request to find
            user specified values for the module, controller, action, and optional
            parameters. It then enters a dispatch loop, dispatching the request.
        </para>

        <para>
            At the beginning of each iteration, it sets a flag in the request
            object indicating that the action has been dispatched. If an action
            or pre or postDispatch plugin resets that flag, the dispatch loop will
            continue and attempt to dispatch the new request. By changing the
            controller and/or action in the request and resetting the dispatched
            flag, the developer may define a chain of requests to perform.
        </para>

        <para>
            The action controller method that controls such dispatching is
            <methodname>_forward()</methodname>; call this method from any of the
            <methodname>preDispatch()</methodname>, <methodname>postDispatch()</methodname> or
            action methods, providing an action, controller,
            module, and optionally any additional parameters you may wish to
            send to the new action:
        </para>

        <programlisting language="php"><![CDATA[
public function fooAction()
{
    // forward to another action in the current controller and module:
    $this->_forward('bar', null, null, array('baz' => 'bogus'));
}

public function barAction()
{
    // forward to an action in another controller:
    // FooController::bazAction(),
    // in the current module:
    $this->_forward('baz', 'foo', null, array('baz' => 'bogus'));
}

public function bazAction()
{
    // forward to an action in another controller in another module,
    // Foo_BarController::bazAction():
    $this->_forward('baz', 'bar', 'foo', array('baz' => 'bogus'));
}
]]></programlisting>
    </sect2>

    <sect2 id="zend.controller.dispatcher.subclassing">
        <title>Subclassing the Dispatcher</title>

        <para>
            <classname>Zend_Controller_Front</classname> will first call the router to
            determine the first action in the request. It then enters a dispatch
            loop, which calls on the dispatcher to dispatch the action.
        </para>

        <para>
            The dispatcher needs a variety of data in order to do its work - it
            needs to know how to format controller and action names, where to
            look for controller class files, whether or not a provided module
            name is valid, and an <acronym>API</acronym> for determining if a given request is even
            dispatchable based on the other information available.
        </para>

        <para>
            <classname>Zend_Controller_Dispatcher_Interface</classname> defines the
            following methods as required for any dispatcher implementation:
        </para>

        <programlisting language="php"><![CDATA[
interface Zend_Controller_Dispatcher_Interface
{
    /**
     * Format a string into a controller class name.
     *
     * @param string $unformatted
     * @return string
     */
    public function formatControllerName($unformatted);

    /**
     * Format a string into an action method name.
     *
     * @param string $unformatted
     * @return string
     */
    public function formatActionName($unformatted);

    /**
     * Determine if a request is dispatchable
     *
     * @param  Zend_Controller_Request_Abstract $request
     * @return boolean
     */
    public function isDispatchable(
        Zend_Controller_Request_Abstract $request
    );

    /**
     * Set a user parameter (via front controller, or for local use)
     *
     * @param string $name
     * @param mixed $value
     * @return Zend_Controller_Dispatcher_Interface
     */
    public function setParam($name, $value);

    /**
     * Set an array of user parameters
     *
     * @param array $params
     * @return Zend_Controller_Dispatcher_Interface
     */
    public function setParams(array $params);

    /**
     * Retrieve a single user parameter
     *
     * @param string $name
     * @return mixed
     */
    public function getParam($name);

    /**
     * Retrieve all user parameters
     *
     * @return array
     */
    public function getParams();

    /**
     * Clear the user parameter stack, or a single user parameter
     *
     * @param null|string|array single key or array of keys for
     *        params to clear
     * @return Zend_Controller_Dispatcher_Interface
     */
    public function clearParams($name = null);

    /**
     * Set the response object to use, if any
     *
     * @param Zend_Controller_Response_Abstract|null $response
     * @return void
     */
    public function setResponse(
        Zend_Controller_Response_Abstract $response = null
    );

    /**
     * Retrieve the response object, if any
     *
     * @return Zend_Controller_Response_Abstract|null
     */
    public function getResponse();

    /**
     * Add a controller directory to the controller directory stack
     *
     * @param string $path
     * @param string $args
     * @return Zend_Controller_Dispatcher_Interface
     */
    public function addControllerDirectory($path, $args = null);

    /**
     * Set the directory (or directories) where controller files are
     * stored
     *
     * @param string|array $dir
     * @return Zend_Controller_Dispatcher_Interface
     */
    public function setControllerDirectory($path);

    /**
     * Return the currently set directory(ies) for controller file
     * lookup
     *
     * @return array
     */
    public function getControllerDirectory();

    /**
     * Dispatch a request to a (module/)controller/action.
     *
     * @param  Zend_Controller_Request_Abstract $request
     * @param  Zend_Controller_Response_Abstract $response
     * @return Zend_Controller_Request_Abstract|boolean
     */
    public function dispatch(
        Zend_Controller_Request_Abstract $request,
        Zend_Controller_Response_Abstract $response
    );

    /**
     * Whether or not a given module is valid
     *
     * @param string $module
     * @return boolean
     */
    public function isValidModule($module);

    /**
     * Retrieve the default module name
     *
     * @return string
     */
    public function getDefaultModule();

    /**
     * Retrieve the default controller name
     *
     * @return string
     */
    public function getDefaultControllerName();

    /**
     * Retrieve the default action
     *
     * @return string
     */
    public function getDefaultAction();
}
]]></programlisting>

        <para>
            In most cases, however, you should simply extend the abstract class
            <classname>Zend_Controller_Dispatcher_Abstract</classname>, in which each of
            these have already been defined, or
            <classname>Zend_Controller_Dispatcher_Standard</classname> to modify
            functionality of the standard dispatcher.
        </para>

        <para>
            Possible reasons to subclass the dispatcher include a desire to
            use a different class or method naming schema in your action
            controllers, or a desire to use a different dispatching paradigm
            such as dispatching to action files under controller directories
            (instead of dispatching to class methods).
        </para>
    </sect2>
</sect1>
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