iOS common objects

Question

I'm writing an iOS app where there is a common object that all views within the app need to access.

I have been creating, and initialising the object within the viewDidLoad event (of the first view controller), and then passing a reference to this object to all other views that need it. This does not seem like the correct way to do things, feels like I'm somehow breaking the MVC pattern since I'm relying that this particular view is always the first to load in order to setup objects that the whole application needs.

I have now modified my app to do the basic object creation and initialisation in the appDelegate "didFinishLaunching...". This is now working and I can access this common object from all of my other views without having to pass around a reference from one view to the other.

Before I go and continue too far, I was hoping to get peoples input on whether this is the correct way to do things, or whether I should be doing anything else? Sorry if this seems like a trivial question, I'm just learning and want to learn how to do things properly.

Thanks in advance :-)

Answer 1

Without repeating what has already been answered, I'd suggest you make your own Singleton object to hold your 'globals', so you don't clutter your AppDelegate with it.

@interface MyGlobalDataController : NSObject

@property (nonatomic, strong) MyData *myData;

+(MyGlobalDataController *)sharedInstance;

@end

@implementation MyGlobalDataController

static MyGlobalDataController *MyGlobalDataControllerSharedInstance = nil;

- (id)init {
    self = [super init];
    if (self) {
        // do whatever needs doing 
    }
    return self;
}

+(MyGlobalDataController *)sharedInstance {
    @synchronized(self) {
        if (MyGlobalDataControllerSharedInstance == nil) {
            MyGlobalDataControllerSharedInstance = [[MyGlobalDataController alloc] init];
        }
    }
    return MyGlobalDataControllerSharedInstance;
}

@end

The first time you access your sharedInstance, the init will be called, so you don't have to worry about timing there.