Question

I was reading this to understand zend’s MVC Request Lifecycle.
But i can’t think of any cases in zend where i would use a controller’s predispatch method , isn’t the init method enough for the code that i want executed before controller’s actions .

What should exactly should be in a controller’s predispatch and not init .

Can you give an example ?

Answer 1

See Zend_Controller_Action – Object Initialization and the following section Pre and Post Dispatch Hooks. They both go into some detail on the two, and the Action Controller itself.

init() is more for setting up the controller object and doing initialization that will be available to all of your actions. Since init() runs prior to preDispatch(), anything you set up in init() will be available for preDispatch() to use. While it is possible to forward or redirect from init(), it is best practice to do it from preDispatch() because it runs prior to dispatching the controller action.

From the manual:

Note: Usage of init() vs. preDispatch() What is the difference between them (init and preDispatch), and what actions would you take
in each?

The init() method is primarily intended for extending the
constructor. Typically, your constructor should simply set object
state, and not perform much logic. This might include initializing
resources used in the controller (such as models, configuration
objects, etc.), or assigning values retrieved from the front
controller, bootstrap, or a registry.

The preDispatch() method can also be used to set object or
environmental (e.g., view, action helper, etc.) state, but its primary
purpose is to make decisions about whether or not the requested action
should be dispatched. If not, you should then _forward() to
another action, or throw an exception.

Note: _forward() actually will not work correctly when executed from init(), which is a formalization of the intentions
of the two methods.