三种创建方式：
1.通过alloc init 方式创建线程并执行
NSThread *thread1 = [[NSThread alloc]initWithTarget:self selector:@selector(runThread) object:nil];
[thread1 setName:@"Namethread1"];//获取线程name [NSThread currentThread].name;可用于判断线程问题
[thread1 setThreadPriority:0.5];//线程优先级，越大优先级越高
[thread1 start];
- (void)runThread{//子线程
for (int i = 0,i<10,i++){
NSLog(@"%d",i);
sleep(1);
if(i=10){//如果i为10的话，回到主线程
[self performSelectorOnMainThread:@selector(runMainThread) withObject:nil waitUntilDone:YES];
}
}
}
- (void)runMainThread{
NSLog(@"回到主线程");
}
2.通过 detachNewThreadSelector 创建线程并执行
[NSThread detachNewThreadSelector:@selector(runThread) toTarget:self withObject:nil];
3.通过 performSelectorInBackground 创建线程并执行
[self performSelectorInBackground:@selector(runThread) withObject:nil];
加锁：
1.@synchronized(self){
}
2.NSCondiction *condition = [[NSCondiction alloc]init];
[condition lock];
[condition unlock];
3.nslock