How to write the method to execute after completion of two methods (ios)

Question

I have 2 methods to be executed on a button click event say method1: and method2: .Both have network calls and so cannot be sure which one will fin

Answer 1

You could just use a flag (aka a BOOL variable) that lets you know in either methods (A or B) if the other one has completed yet. Something on the lines of this:

- (void) methodA
{
    // implementation

    if (self.didFinishFirstMethod) {
        [self finalMethod];
    } else {
        self.didFinishFirstMethod = YES;
    }
}


- (void) methodB
{
    // implementation

    if (self.didFinishFirstMethod) {
        [self finalMethod];
    } else {
        self.didFinishFirstMethod = YES;
    }
}


- (void) finalMethod
{
    // implementation
}

Cheers!

Answer 2

Neat little method I got from Googles iOS Framework they rely on pretty heavily:

- (void)runSigninThenInvokeSelector:(SEL)signInDoneSel {


    if (signInDoneSel) {
        [self performSelector:signInDoneSel];
    }

}

Answer 3

This is what dispatch groups are for.

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t group = dispatch_group_create();

// Add a task to the group
dispatch_group_async(group, queue, ^{
  [self method1:a];
});

// Add another task to the group
dispatch_group_async(group, queue, ^{
  [self method2:a];
});

// Add a handler function for when the entire group completes
// It's possible that this will happen immediately if the other methods have already finished
dispatch_group_notify(group, queue, ^{
   [methodFinish]
});

Dispatch groups are ARC managed. They are retained by the system until all of their blocks run, so their memory management is easy under ARC.

See also dispatch_group_wait() if you want to block execution until the group finishes.