Understanding how app delegates and view controllers relate to each other

Question

I'm tryin to grasp the fundamentals of Cocoa (Iphone) MVC design, but it's being quite tough. I've come accross several example applications, from the web, books.. but I've found nothing related to what I'm searching, since most of the examples just present a simple app (ie, a viewcontroller with a flipside viewcontr and a bit more..). So let's see if someone is willing to help me out in pointing me to the right direction:

• My goal is to build a somewhat complex app. I'd like to have the following relation of views:

  1. Presentation view (which would have a controller loading several memory intensive vars)

  2. Main menu view: different options that would result in entirely new complex views. In example, a Begin option to initiate whatever the app permits to do; a second option to do another complex task with different views and actions within it, an Options option to configure options; a help option, an about option, etcetera..

• In a first approach I tried to embed several rounded buttons in a view under the MainWindow nib with an associated app delegate. This approach though posed the question to how I manage to switch between views/viewcontrollers. After having uncaught exceptions because I probably don't fully understand the basics, I tried to move on to more 'simple' things.

• Then I came accross the Navigation and Tabbar default Cocoa controllers. I don't want a tabbar, although it could come well for other parts of this app. Then the nav controller is what I think is most suitable for this case.

• Thus, am I on the right spot if I build a hierarchichal app where its root is a nav controller? I've seen I can customize the main view to display a customized table, where each cell coud act as a button to spawn its respective view+viewcontroller. From here then I can keep building the 'leaf nodes' of this hierarchy of views/viewcontrollers, right? Eventhough I don't like the animation that by default provides the nav controller, I assume I can get rid off it..

• So to sum it up in an easy way: I'd like to obtain a menu like those that can usually be seen on Cocos2d apps.

It's frustrating to ask this, I know it has to be easy but I find the documentation quite a mess aswell as the examples I've seen.. GUI programming it's being a tough learning curve :/

Thank you for any answers in advance, and excuse me for this long post.

Answer 1

Thus, am I on the right spot if I build a hierarchichal app where its root is a nav controller?

Almost. A nav controller (despite being a subclass of UIViewController) does not control views but rather other view controllers. The nav controller pushes and pops the view controllers which in turn causes the controller's respective views to load and become visible.

Therefore, the "root view" is actually the view that is controlled by the view controller that is in the nav controller topViewController property.

The app delegate serves to hold the nav controller and to tell it which view controller to push on the stack first. After that, the view controllers tell the nav controller when to push and pop them.

Otherwise, you're on the right track. You should always attempt to present information on a mobile platform in an hierarchal manner starting with the most general at the top and growing more specific as you drill down.

And you shouldn't be embarrassed at finding this confusing. 90% of the introductory/tutorial info out there, including books and Apple resources, focus on the gee whiz aspects of the interface and tell you next to nothing about the actual application design or how all the parts fit together conceptually.

Answer 2

You right about how little information is covered about app delegates to nav controllers. I been digging and trying to get all my screens linking etc. Having alot of fun watching my apps start to look more then just some Frankenstein monster UI. ahahah

The Itunes dev videos are great for looking at push and pop stack UIviews theory. I found they moved a little fast but after watching them the hands did make more sense. I have been forcing myself to watch them all and get a really good feel for whats going on. Hopefully have a nice app working soon.