Varien action dispatch design, allows developers to seamlessly prevent dispatch, forward request to different action, or simply redirect. First step in accomplishing this is creating a pre-dispatch event observer for desired action.
In our example, we will prevent logged out users from accessing cart page:
If we now try to access cart page as a guest customer, we should expect to be redirected to login page instead. However, this is not the case due to core bug within
Lastly, we have to move core file to local code pool and correct the bug: