NSThread中使用锁相关的笔记

1.创建NSThread对象和NSLock或者NSCondition对象

- (IBAction)touchUpInsideByThreadOne:(id)sender {
    tickets = 100;
    count = 0;
    theLock = [[NSLock alloc] init];
    // 锁对象
    ticketsCondition = [[NSCondition alloc] init];
    
    ticketsThreadone = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadone setName:@"Thread-1"];
    [ticketsThreadone start];
    
    
    ticketsThreadtwo = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadtwo setName:@"Thread-2"];
    [ticketsThreadtwo start];
}

2.相关资源锁的用法

- (void)run{
    while (TRUE) {
        //加锁方法一，使用条件锁
        [ticketsCondition lock];
        if(tickets >= 0){
            [NSThread sleepForTimeInterval:0.09];
            count = 100 - tickets;
            NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
            tickets--;
        }else{
            break;
        }
        [ticketsCondition unlock];
        
        //加锁方法二，使用NSLock对象
        [theLock lock];
        if(tickets >= 0){
            [NSThread sleepForTimeInterval:0.09];
            count = 100 - tickets;
            NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
            tickets--;
        }else{
            break;
        }
        [theLock unlock];
        
        //加锁方法三，使用@synchronized(self)
        @synchronized(self)
        {
            if(tickets >= 0){
                [NSThread sleepForTimeInterval:0.09];
                count = 100 - tickets;
                NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
                tickets--;
            }else{
                break;
            }
        }
    }
}

如果没有线程同步的lock，卖票数可能是-1.加上lock之后线程同步保证了数据的正确性。以上均是0.09S执行一次。

3.使用NSConditioniLock中的signal和wait控制线程1和2的执行频率，即使用线程3去唤醒其他两个线程锁中的wait。

- (IBAction)touchUpInsideByThreadOne:(id)sender {
    tickets = 10;
    count = 0;
    theLock = [[NSLock alloc] init];
    // 锁对象
    ticketsCondition = [[NSCondition alloc] init];
    ticketsThreadone = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadone setName:@"Thread-1"];
    [ticketsThreadone start];
    
    ticketsThreadtwo = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadtwo setName:@"Thread-2"];
    [ticketsThreadtwo start];
    
    NSThread *ticketsThreadthree = [[NSThread alloc] initWithTarget:self selector:@selector(run3) object:nil];
    [ticketsThreadthree setName:@"Thread-3"];
    [ticketsThreadthree start];
}

-(void)run3{
    while (YES) {
        [ticketsCondition lock];
        [NSThread sleepForTimeInterval:1];
        [ticketsCondition signal];
        [ticketsCondition unlock];
    }
}

- (void)run{
    while (TRUE) {
        // 上锁
        [ticketsCondition lock];
        [ticketsCondition wait];
        [theLock lock];
        if(tickets >= 0){
            [NSThread sleepForTimeInterval:0.09];
            count = 10 - tickets;
            NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
            tickets--;
        }else{
            break;
        }
        [theLock unlock];
        [ticketsCondition unlock];
    }
}

参考：http://www.uml.org.cn/mobiledev/201210262.asp