How to program navigation in a MVC application? (help please!!)

Question

Hi,
I´m exploring how to develop a BSP application with MVC.
SO far I have a ´page´ composed by a controller, 2 or more sub-controllers and their respective views.
But I want an application consisting of many pages.. So here I am, in my DO_HANDLE_EVENT method wandering what to do when I want to redirect the user to a new page. I guess there´s two options here:
1) change the subcontrollers/views for the new one. (using controller_set_active or controller_delete..?)
2) redirecting to the new page with navigation->goto_page( 'page2.do' ).
I like the second option, but there´s a problem: all my model instances die!! How can I keep them alive? How can I keep data (objects) alive from the moment a user opens the first page till he logs off the aplication??
(I tried using the application class, but I just can´t access it using MVC, guess it´s only available from pages with flow logic)
I truly need a hint on this! Any suggestions are most welcomed!

Answer 1

Hi Mariana,
I think the most important advice is to never jump
directly via goto_page(). As you have noted, this way
you lose your context. Myself I use the following
approach:
1) There is a strict controller hierarchy. The topmost
   controller holds your application data.
2) In the view of the topmost controller its
   subcontrollers are called via
      <bsp:call url="sub.do" comp_id="yourchoicehere" >
               <bsp:parameter name = "mode"
                              value = "<%=mode%>" />
      </bsp:call>
   where "mode" is an attribute of the view which holds
   the information in which state of processing your
   application is.
3) In the controllers in the DO_REQUEST methods
   you call its views by
   dispatch_input( ).
   l_main_view = create_view( view_name = 'main_view.htm' ).
  l_main_view->set_attribute( name = 'mode' value = mode ).
  call_view( l_main_view ).
  The dispatch_input method is only needed in the
  topmost controllers.
4) Navigation is done by events which are passed
   automatically to the DO_HANDLE_EVENT method of
   the controller.
   IF htmlb_event IS BOUND.
      CASE htmlb_event->server_event.
        WHEN 'YOUREVENTHERE'.
5) To understand how things work you should set
   breakpoints in all DO_HANDLE_EVENT and DO_REQUEST
   methods. You will see how events got passed upwards
   the controller hierarchy and how controllers call
   their subcontrollers.
6) Further hint: Pass all parameters by controller
   and view attributes.
Hope that helps.
Joachim