How do I share an object between UIViewControllers on iPhone?

Question

My application is a tab bar application, with a separate view controller for each tab.

I have an object in my first view controller (A) which contains all my stored

Answer 1

I like to create a top level Model class that is a singleton and contains all the elements I might need.

It's helpful to also give it a top level load method that populates objects with just the db keys, using the hydrate/dehydrate pattern common in the Apple examples.

Typical usage in the app delegate would be simply,

[[MyModel sharedModel] load];

And then in a view controller:

NSArray *myThing1s = [[MyModel sharedModel] thing1s];
NSArray *myThing2s = [[MyModel sharedModel] thing2s];

You can then iterate over your thing1s and thing2s and when you need details, you can just call

[myThing1 hydrate];

which will populate the object.

Of course, you probably want to use CoreData to manage the persistence from 3.0 onwards.