iOS開發CGD買票

@interface ViewController ()
{
    int _totalCount; // 火車票總票數
    int _surplusCoynt; // 剩餘票數
    NSLock *_lock; // 互斥鎖
}

@end

// 設置剩餘票數
    _surplusCoynt = 100;

    _lock = [[NSLock alloc] init]; // 創建互斥鎖，多個線程共享使用


    // 自己創建並行隊列
    dispatch_queue_t queue1 = dispatch_queue_create("火車站", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(queue1, ^{
        [self saleTickets:queue1];
    });

    dispatch_queue_t queue2 = dispatch_queue_create("代售點", 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]; // 獲取互斥鎖並且添加
        const charchar *queueLabel = dispatch_queue_get_label(queue);
        NSString *label = [NSString stringWithUTF8String:queueLabel];
        NSLog(@"當前火車票由%@售出，餘票:%d張", label, _surplusCoynt);
        _surplusCoynt--;
        [_lock unlock];
    }
}