小驴拉磨之iOS进阶-多线程（6）—— GCD 并发队列

并发队列，异步执行

//MARK:并发队列，异步执行
-(void)GCDSerialQueuesfour{
    
    //1.队列-并发 DISPATCH_QUEUE_CONCURRENT 并发
    dispatch_queue_t  q = dispatch_queue_create("cc_queue",DISPATCH_QUEUE_CONCURRENT);
    
    //2.异步执行任务
    for(int i = 0;i < 10;i++)
    {
        dispatch_async(q,^{
            NSLog(@"%@ %d",[NSThread currentThread],i);
        });
    }
    
    NSLog(@"come here");
    
}

• 打印结果

2017-11-16 14:25:17.299034+0800 GCDDome-串行队列[4319:2567001] come here
2017-11-16 14:25:17.299172+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 0
2017-11-16 14:25:17.299226+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 2
2017-11-16 14:25:17.299258+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 3
2017-11-16 14:25:17.299299+0800 GCDDome-串行队列[4319:2567029] <NSThread: 0x1c0661f00>{number = 4, name = (null)} 1
2017-11-16 14:25:17.299313+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 4
2017-11-16 14:25:17.299342+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 5
2017-11-16 14:25:17.299378+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 6
2017-11-16 14:25:17.299403+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 7
2017-11-16 14:25:17.299427+0800 GCDDome-串行队列[4319:2567027] <NSThread: 0x1c4264680>{number = 3, name = (null)} 8
2017-11-16 14:25:17.300349+0800 GCDDome-串行队列[4319:2567029] <NSThread: 0x1c0661f00>{number = 4, name = (null)} 9

• 总结

会开多条线程，线程数量是由GCD来决定
不会顺序执行
come here的位置不确定，一般会靠上的位置

并发队列，同步执行

//MARK:并发队列，同步执行
-(void)GCDSerialQueuesFive{
    
    //1.队列-并发 DISPATCH_QUEUE_CONCURRENT 并发
    dispatch_queue_t  q = dispatch_queue_create("cc_queue",DISPATCH_QUEUE_CONCURRENT);
    
    //2.同步执行任务
    for(int i = 0;i < 10;i++)
    {
        dispatch_sync(q,^{
            NSLog(@"%@ %d",[NSThread currentThread],i);
        });
    }
    
    NSLog(@"come here");
    
}

• 打印结果

2017-11-16 14:30:00.932762+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 0
2017-11-16 14:30:00.932816+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 1
2017-11-16 14:30:00.932840+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 2
2017-11-16 14:30:00.932862+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 3
2017-11-16 14:30:00.932883+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 4
2017-11-16 14:30:00.932904+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 5
2017-11-16 14:30:00.932925+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 6
2017-11-16 14:30:00.932945+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 7
2017-11-16 14:30:00.932969+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 8
2017-11-16 14:30:00.933010+0800 GCDDome-串行队列[4322:2569434] <NSThread: 0x1c0074ac0>{number = 1, name = main} 9
2017-11-16 14:30:00.933019+0800 GCDDome-串行队列[4322:2569434] come here

• 总结

不会开几条线程
会顺序执行
come here在最后的位置

小结

开不开线程，取决去任务的函数，同步不开，异步才能开；
开几条线程，取决于队列，串行开一条，并发可以开多条（异步执行）