Adding delay between execution of two following lines

I need to add a delay between the execution of two lines in a(same) function. Is there any favorable option to do this?

Note: I don't need two different functions to do this, and the delay must not affect other functions' execution.

eg:

line 1: [executing first operation];

line 2: Delay                        /* I need to introduce delay here */

line 3: [executing second operation];

Any help is appreciable. Thanks in advance...

Solution 1:

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

Solution 2:

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)

Solution 3:

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);
}