iphone - How to cancel/exit/stop execution of Thread object or thread running in background in IOS

Question

I detaching The thread as given below to do some operation in background

 currentThread = [[NSThread   alloc]initWithTarget:contactServiceselector:@selector(requestForContactBackup:)object:msisdn];

 [currentThread start];

This currentThread is the pointer of AppDelegate. I have one button on my view and when i will press it I want to cancel or stop the execution of background thread.

To do This something like this:

-(void)cancelTheRunningTasks {

   if(self.currentThread !=nil) {

        [currentThread cancel];
        NSLog(@"IsCancelled: %d",[currentThread isCancelled]);   //here Yes returns
        [self removeNetworkIndicatorInView:backUpViewController.view];
    }  
}

Problem with that the background thread is still under execution.

With my thread refrence how to cancel/stop execution/kill the background thread from main thread ?

please refer some solutions. Thanks.

Answer 1

Your background thread needs to check to see if it has been cancelled, either through the isCancelled method...

if ([[NSThread currentThread] isCancelled]) {
    // do cleanup here
    [NSThread exit];
}

You can't kill the thread externally because there is no way to know what state the thread might be in and, thus, killing it would produce indeterminate behavior (imagine if the thread was holding a mutex down in the allocator when it was killed... ouch).