Adding delay between execution of two following lines

You can use gcd to do this without having to create another method

// ObjC

NSTimeInterval delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
  NSLog(@"Do some work");
});

// Swift

DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
    print("Do some work)
}

You should still ask yourself "do I really need to add a delay" as it can often complicate code and cause race conditions

You can use the NSThread method:

[NSThread sleepForTimeInterval: delay];

However, if you do this on the main thread you'll block the app, so only do this on a background thread.

---

or in Swift

NSThread.sleepForTimeInterval(delay)

in Swift 3

Thread.sleep(forTimeInterval: delay)

I have a couple of turn-based games where I need the AI to pause before taking its turn (and between steps in its turn). I'm sure there are other, more useful, situations where a delay is the best solution. In Swift:

        let delay = 2.0 * Double(NSEC_PER_SEC) 
        let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay)) 
        dispatch_after(time, dispatch_get_main_queue()) { self.playerTapped(aiPlayView) }

I just came back here to see if the Objective-C calls were different.(I need to add this to that one, too.)

This line calls the selector secondMethod after 3 seconds:

[self performSelector:@selector(secondMethod) withObject:nil afterDelay:3.0 ];

Use it on your second operation with your desired delay. If you have a lot of code, place it in its own method and call that method with performSelector:. It wont block the UI like sleep

Edit: If you do not want a second method you could add a category to be able to use blocks with performSelector:

@implementation NSObject (PerformBlockAfterDelay)

- (void)performBlock:(void (^)(void))block 
          afterDelay:(NSTimeInterval)delay
{
    block = [block copy];
    [self performSelector:@selector(fireBlockAfterDelay:) 
               withObject:block 
               afterDelay:delay];
}

- (void)fireBlockAfterDelay:(void (^)(void))block
{
    block();
}

@end

Or perhaps even cleaner:

void RunBlockAfterDelay(NSTimeInterval delay, void (^block)(void))
{
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC*delay),
      dispatch_get_current_queue(), block);
}