Questiong in using a model class

Question

I'm pretty new with the MVC design pattern. When using the model class, I don't know what is the more advantages of using the model class instead of using an application class.
Moreover, in my application, there are two pages. One is used for searching screen, and the other is used for displaying a result. I try to use the model class to receive all input parameters passed by the view. Everything is fine. After users clicks a search button, a search controller will call the subcontroller which displays a result. At this point, I cannot figure out the best place where calling subcontroller should be. Right now, I put it in the do_request method; nevertheless, I have to detect the search event in this do_request method, as well. In my view, it seems strange! Are there any other solutions or examples matching my problem.

Answer 1

MVC design pattern is to seperate out different logic. and at the same time keeping them as a seperate entity so that they can be used multiple times(reusability) in different controllers or so.
yes it is posible to implement the same using application class. like we can make 1 class for mode(business logic) and one for control(class 2) and now make our application class which will inherit these two. this way it will work fine. but in this  yet we are seperating the business and control logic but we are not able to make the act as a seperate entity. the objects  of their type will be live via application class throughout the application.
and if we make them as a different class instead of inheriting them in application class, and instatiate them whenever require, then that is MVC, that is what we are doing. we are just bypassing application class since we can directly use  class of controller type(super class CL_BSP_CONTROLLER).
there is no such heirarchy type layering in MVC, these are like three different objects and we are making them communicate to each other so that functionality of each can be seperate out.
hope this clears your doubt.
there is a application like you are looking for:
check it:
http://help.sap.com/saphelp_erp2004/helpdata/en/12/1eeeb4245d1f4f96c989519261b0f6/frameset.htm
it is in sap as : bsp application : TUTORIAL_4_MVC  
it has a controller for searhing search.do
hope this helps,
regards,
Hemendra