How to stop a NSThread sub-thread in iphone

Q:

I created a sub-thread using NSThread in main thread

NSThread *newThread = [[NSThread alloc] initWithTarget:self selector:@selector(MyThread:) object:timer];

5 sec later,i used [newThread cancel] in main thread to stop the sub-thread,but it didnt work,

Method MyThread: in newThread still working

so,whats the correct answer to stop newThread,THX

A:

cancal method only informs the thread that it is cancelled (as you mentioned changes theisCancelled to YES. It's then the responsibility of the thread itself to check this and exit. For example, in your MyThread: method you could do this:

// At some checkpoint
if([[NSThread currentThread] isCancelled]) {
    /* do some clean up here */
    [NSThread exit];
}

You should do this check periodically, and exit from within the thread as shown; otherwise the canceldoesn't have any effect.

@None: It means that "cancelling" a thread doesn't do what you think. When you cancel a thread, it causes isCancelled to return YES. The thread should then stop executing. It doesn't force the thread to immediately stop execution, though — that would be troublesome if it had any resources open