How can I access data that's stored in my App Delegate from my various view controllers?

Question

This question is similar to this other post, but I'm new to iPhone development and I'm getting used to the good practices for organizing my data throughout my app. I understand the ApplicationDelegate object to be the best place to manage data that is global to my app, correct? If so, how can I access data that's stored in my App Delegate from various view controllers? For example, my array is created in the app delegate as such...

appdelegate.m

sectionTitles = [[NSArray alloc] initWithObjects: @"Title1", @"Title2", @"Title3", nil];
rootViewController.appDelegate = self;

and I need to access it throughout the different views of my app, like my root table view controller...

rootviewcontroller.m

NSUInteger numTableSections = [self.appDelegate.sectionTitles count];

Is this the best way to do it or are there any reasons I should organize my data a better way? I ask because I can never really get too comfortable with using global variables (I blame my college professors), though I'm not sure if this can be considered a global variable.

Thanks so much in advance for your help!

Answer 1

This should work:

self.appDelegate = ( YourApplicationDelegate *) [[UIApplication sharedApplication] delegate];

Answer 2

I understand the ApplicationDelegate object to be the best place to manage data that is global to my app, correct?

Not really (your college professors had a point). It's tempting to start putting a lot of stuff into the app delegate, but it's not a very sustainable practice. See my answer here.

And read this good post by Matt Gallagher for more depth.

That said, I often put something like this in my app delegate header:

#define APP_DELEGATE (MyAppDelegate*) [[UIApplication sharedApplication] delegate]

so I can easily do things like:

int n = [[APP_DELEGATE sectionTitles]count];