Objective-C, running NSTask in background periodically

Question

I've seen some good information on how to keep an NSTask running in the background, although that's not entirely what I want to do. What I would like to do is periodically run an NSTask in the the background (like every 30 seconds), then kill it; here might be one example of what I would like to do:

NSTask *theTask = [ [ NSTask alloc ] init ];
NSPipe *taskPipe = [ [ NSPipe alloc ] init ];

[ theTask setStandardError:taskPipe ];
[ theTask setStandardOutput:taskPipe ];
[ theTask setLaunchPath:@"/bin/ls" ];
[ theTask setArguments:[ NSArray arrayWithObject:@"-l" ] ];
[ theTask launch ];

// Wait 30 seconds, then repeat the task

Answer 1

Maybe you can simply put in sleep the thread and wait 30 seconds inside a do loop :

do {

[ theTask launch ]; //Launch the Task
sleep(30);          //Sleep/wait 30 seconds 

} while (someCondition);

Otherwise you could use an NSTimer :

NSTimer *t = [NSTimer scheduledTimerWithTimeInterval: 30.0
                      target: self
                      selector:@selector(onTick:)
                      userInfo: nil repeats:YES];


- (void)onTick:(NSTimer *)timer {
    //In this method that will be get called each 30 seconds, 
    //you have to put the action that you want to perform ...
    [ theTask launch ];
}