CODEWITHSUNDEEP
iphoneobjective-cios
RomanHouse
RomanHouse

Reputation: 2552

How to call method with delay and in background thread

I have a method what I want to call after -viewDidLoad and in background thread. Is there way to combine this two methods:

[self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]

and

[self performSelectorInBackground:(SEL) withObject:(id)]?

Upvotes: 14

Views: 13523

Answers (4)

Robotic Cat
Robotic Cat

Reputation: 5891

Try the following:

// Run in the background, on the default priority queue
dispatch_async( dispatch_get_global_queue(0, 0), ^{
    [self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]
});

Code not tested

Be aware that your selector/method must not use UIKit (so don't update the UI) or access UIKit properties (like frame) so your selector may need to kick off work back to the main thread. e.g.

(id)SomeMethod:UsingParams: {

    // Do some work but the results

    // Run in the background, on the main queue
    dispatch_async(dispatch_get_main_queue(), ^{
        // Do something UIKit related
    });
}

Upvotes: 7

fabrice truillot de chambrier
fabrice truillot de chambrier

Reputation: 5558

You can do that per example:

dispatch_time_t delay = dispatch_time( DISPATCH_TIME_NOW, <delay in seconds> * NSEC_PER_SEC );
dispatch_after( delay, dispatch_get_main_queue(), ^{
    [self performSelectorInBackground: <sel> withObject: <obj>]
});

Somehow a mixed solution. It would be better to stick with a full GCD approach tho.

Upvotes: 2

jscs
jscs

Reputation: 64002

Grand Central Dispatch has dispatch_after() which will execute a block after a specified time on a specified queue. If you create a background queue, you will have the functionality you desire.

dispatch_queue_t myBackgroundQ = dispatch_queue_create("com.romanHouse.backgroundDelay", NULL);
// Could also get a global queue; in this case, don't release it below.
dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC);
dispatch_after(delay, myBackgroundQ, ^(void){
    [self delayedMethodWithObject:someObject];
});
dispatch_release(myBackgroundQ);

Upvotes: 23

graver
graver

Reputation: 15213

[self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]

Performs a selector on the thread that it is being called. So when you call it from a background thread it will run there...

Upvotes: 4

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