iOS疯狂详解之GCD卖火车票

@interface ViewController ()
{
    int _totalCount; // 火车票总票数
    int _surplusCoynt; // 剩余票数
    NSLock *_lock; // 互斥锁
}

@end

// 设置剩余票数
    _surplusCoynt = 100;
    
    _lock = [[NSLock alloc] init]; // 创建互斥锁，多个线程共享使用
    
    
    // 自己创建并行队列
    dispatch_queue_t queue1 = dispatch_queue_create("火车站", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(queue1, ^{
        [self saleTickets:queue1];
    });
    
    dispatch_queue_t queue2 = dispatch_queue_create("代售点", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(queue2, ^{
        [self saleTickets:queue2];
    });

#pragma mark - 售票方法
- (void)saleTickets:(dispatch_queue_t)queue
{
    while (_surplusCoynt > 0) {
        [_lock lock]; // 获取互斥锁并且添加
        const char *queueLabel = dispatch_queue_get_label(queue);
        NSString *label = [NSString stringWithUTF8String:queueLabel];
        NSLog(@"当前火车票由%@售出，余票:%d张", label, _surplusCoynt);
        _surplusCoynt--;
        [_lock unlock];
    }
}