How to pause the execution of While loop in Objective c?

Question

I want to pause the execution of while loop for 200 milliseconds.I have used [NSThread sleepForTimeInterval:0.2] ,It's working fine for me but, I want to know what are the alternative ways to pause execution of while loop?

Answer 1

If it's working fine then no problem, however if you are doing something in the thread that needs the runloop (i.e. NSTimer or NSURLRequest in async mode) then you need to run the runloop, so this would be required:

(tested)

+ (void)runRunLoopForTimeInterval:(NSTimeInterval)timeInterval {
    NSDate *stopTime = [NSDate dateWithTimeIntervalSinceNow:timeInterval];
    while ([stopTime compare:[NSDate date]] == NSOrderedDescending) { 
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                                 beforeDate:stopTime];
    }
}

and call it like this:

[SomeClass runRunLoopForTimeInterval:0.2];

EDIT Some assumptions:

1. The thread is a background thread.
2. You are waiting for something to happen. If so you can use something like RunLoopController which allows that condition to be signalled and will force the run loop to break out before the required time.

Answer 2

Let's imagine we have a while in the following form:

while (... condition ...) {
   ... doSomething ...;

   if (... waitCondition ...) {
      //I want to wait here
   }
}

We will make it asynchronous, first by abstracting things into methods:

- (BOOL)condition {
   //some condition, e.g.
   return (self.counter > 5000);
 }

- (void)doSomething {
   //do something, e.g.
   self.view.alpha = self.counter / 5000.0f;
   self.counter++;
}

- (BOOL)waitCondition {
   // some wait condition, e.g.
   return ((self.counter % 100) == 0);
}

- (void)startWhile {
   //init the state
   self.counter = 0;
   [self performWhile];
}

- (void)performWhile {
   while ([self condition]) {
      [self doSomething];

      if ([self waitCondition]) {
         [self performSelector:@selector(performWhile)
                    withObject:nil
                    afterDelay:0.2
                       inModes:@[NSDefaultRunLoopMode]];
      }
   }
}

Instead of using a global state in self, you can also use a parameter with performWhile.