Delaying a method on a separate thread in objective C

Question

Is there a way to delay a method call before it changes a key value in the user defaults?

For instance; I have method A which is an IBAction and Method B. If a key "keyOne" is false; method A sets "keyOne" to true via the -[NSUserDefaults setBool: forKey:] and then calls method B with an integer input of for time delay. Method B then needs to wait for whatever the delay was input to be in seconds and then change the "keyOne" back to true with the same NSUserDefaults.

score 9 · Accepted Answer · edited May 23 '17 at 12:07

Use GCD's dispatch_after() to delay the operation. But, instead of using the main queue as generated by the Xcode code snippet, create your own queue, or utilize the background queue.

dispatch_queue_t myQueue = dispatch_queue_create("com.my.cool.new.queue", DISPATCH_QUEUE_SERIAL);

double delayInSeconds = 10.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, myQueue, ^(void){

    // Reset stuff here (this happens on a non-main thead)
    dispatch_async(dispatch_get_main_queue(), ^{
        // Make UI updates here. (UI updates must be done on the main thread)
    });
});

You can find more information on the difference between using performSelector: and dispatch_after() in the answer in this post: What are the tradeoffs between performSelector:withObject:afterDelay: and dispatch_after

Thanks for the information on this; just what I had been looking for. Much appreciated! — Timothy Frisch, Feb 13 '14 at 16:20
Now if I add that to my UI and call my UI-updating methods there is still a delay. — Timothy Frisch, Feb 13 '14 at 19:36

score 3 · Answer 2 · answered Feb 13 '14 at 16:14

3

You can use perform selector from method A to call method B:

[self performSelector:@selector(methodName) withObject:nil afterDelay:1.0];

If your method B needs to know the delay you can use withObject: to pass parameter, it needs to be NSNumber, not integer.

answered Feb 13 '14 at 16:14

Greg

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This is exactly what I needed; method B does not need to know the delay it just needs to happen. Thanks for this! – Timothy Frisch Feb 13 '14 at 16:15
@Tukajo If you think this answer helped you, please mark it as the right answer. – Anindya Sengupta Feb 13 '14 at 16:19
Can't until after a certain time limit @Anindya Sengupta ;) – Timothy Frisch Feb 13 '14 at 16:20
2

Grand Central Dispatch is the better route to go, so the other answer is probably the one you want to go with. – Gavin Feb 13 '14 at 16:22

Delaying a method on a separate thread in objective C

2 Answers2