Question

I used the code below to wait for NSTimer triggered

    -(void)timer1Fired :(NSTimer *) timer
    {

    isTriggered=true;

    }


    //----------------------------------------------
    isTriggered=false;

    [NSTimer scheduledTimerWithTimeInterval:1  
                                 target:self
                               selector:@selector(timer1Fired:)
                               userInfo:nil
                                repeats:NO];






    int j1 = 0;
    while ( !isTriggered && j1 <   1000)
    {

        [NSThread sleepForTimeInterval: 0.5];

        j1++;

    }
    //continue to do  something   //b

but it looks like NSTimer never be triggered

Welcome any comment

Answer 1

I don’t think [NSThread sleepFortimeInterval] does what you expect it to do. You’re right, isTriggered: will not be executed until after your 500 second long while loop has finished.

Also, NSTimer and NSThread are both old fashioned and you should be using Grand Central Dispatch instead (to replace both of them). GCD is significantly faster and uses less resources, and it is also more reliable/powerful.

https://developer.apple.com/library/mac/#documentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

  // do stuff on background thread

  dispatch_sync(dispatch_get_main_queue(), ^{

    // do stuff on main thread

  });
});

If you want to avoid using a low level C API, you can use NSOperation and NSOperationQueue, which are high level wrappers for GCD.