NSTimer callback on background thread

Question

I have a NSTimer defined as follows:

timer = [NSTimer scheduledTimerWithTimeInterval:30
                                         target:self
                


        

Answer 1

You are adding the timer to main thread. Your call back will also be in main thread. To schedule the timer in a background thread, I think you need to use NSOperation subclass and schedule the timer to [NSRunLoop currentRunLoop] from inside the operation's main method.

#import 

@interface BackgroundTimer : NSOperation
{
    BOOL _done;
}
@end



#import "BackgroundTimer.h"

@implementation BackgroundTimer

-(void) main
{
    if ([self isCancelled])
    {
        return;
    }

    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:30
                                             target:self
                                           selector:@selector(fooBar)
                                           userInfo:nil
                                            repeats:YES];

    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

    //keep the runloop going as long as needed
    while (!_done && [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                                              beforeDate:[NSDate distantFuture]]);

}

@end