Adding delay between execution of two following lines

Question

I need to add delay between the execution of two lines in a same  function  Is there is any favorable options 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

User · Accepted Answer

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

double 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");
});

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

User · Answer

If you re targeting iOS 4 0   you can do the following    executing first operation   double 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        executing second operation

User · Answer

checked 27 Nov 2020 and confirmed to be still accurate with Xcode 12 1  The most convenient way these days  Xcode provides a code snippet to do this where you just have to enter the delay value and the code you wish to run after the delay   click on the   button at the top right of Xcode  search for after It will return only 1 search result  which is the desired snippet  see screenshot   Double click it and you re good to go

User · Answer

Like  Sunkas wrote  performSelector withObject afterDelay  is the pendant to the dispatch after just that it is shorter and you have the normal objective-c syntax  If you need to pass arguments to the block you want to delay  you can just pass them through the parameter withObject and you will receive it in the selector you call    self performSelector  selector testStringMethod               withObject   Test Test              afterDelay 0 5    -  void testStringMethod  NSString   string      NSLog   string   gt  gt  gt       string       If you still want to choose yourself if you execute it on the main thread or on the current thread  there are specific methods which allow you to specify this  Apples Documentation tells this      If you want the message to be dequeued when the run loop is in a mode   other than the default mode  use the   performSelector withObject afterDelay inModes  method instead  If you   are not sure whether the current thread is the main thread  you can   use the performSelectorOnMainThread withObject waitUntilDone  or   performSelectorOnMainThread withObject waitUntilDone modes  method to   guarantee that your selector executes on the main thread  To cancel a   queued message  use the cancelPreviousPerformRequestsWithTarget  or   cancelPreviousPerformRequestsWithTarget selector object  method

User · Answer

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

User · Answer

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

User · Answer

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

[objective-c] Adding delay between execution of two following lines

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