在下面的例子中 使用 NSLock 使得 线程A，B，C， 依次执行；若不使用NSLock 则线程的执行是无序的<span style="font-family: Arial, Helvetica, sans-serif;">// NSLock的执行原理：</span>
<span style="font-family: Arial, Helvetica, sans-serif;">// 某个线程A调用lock方法。这样，NSLock将被上锁。可以执行“关键部分”，完成后，调用unlock方法。</span>
// 如果，在线程A 调用unlock方法之前，另一个线程B调用了同一锁对象的lock方法。那么，线程B只有等待。直到线程A调用了unlock。
NSLock* _lock = [[NSLock alloc] init];
// ThreadA
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
[_lock lock];
[self performSelector:@selector(threadA) withObject:nil];
sleep(5);
[_lock unlock];
});
// ThreadB
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
[_lock lock];
[self performSelector:@selector(threadB) withObject:nil];
sleep(5);
[_lock unlock];
});
// ThreadC
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
[_lock lock];
[self performSelector:@selector(threadC) withObject:nil];
sleep(5);
[_lock unlock];
});
}
- (void)threadA
{
NSLog(@"name A: %@",[NSThread currentThread].name);
}
- (void)threadB
{
NSLog(@"name B: %@",[NSThread currentThread].name);
}
- (void)threadC
{
NSLog(@"name C: %@",[NSThread currentThread].name);
}
