CGD小计

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GCD代码记录，以便后用

//自定义一个queue：- (void)customQueue{    /*     第二个参数传：     串行队列：DISPATCH_QUEUE_SERIAL     开启一个子线程，按序执行     并行队列：DISPATCH_QUEUE_CONCURRENT 开启多个子线程，无序执行     同步：串行、并行都会在主线程     异步：串行、并行都会在子线程     */    //串行队列    dispatch_queue_t serialQueue = dispatch_queue_create("com.gcd.serialQueue", DISPATCH_QUEUE_SERIAL);    //并发队列    dispatch_queue_t concurrentQueue = dispatch_queue_create("com.gcd.concurrentQueue", DISPATCH_QUEUE_CONCURRENT);//可以通过dispatch_queue_get_label(dispatch_queue_t queue)获取你创建queue的名字    const char *c = dispatch_queue_get_label(concurrentQueue);    NSLog(@"%s",c);//com.gcd.concurrentQueue    dispatch_sync(concurrentQueue, ^{        NSLog(@"1");        [NSThread sleepForTimeInterval:2];        NSLog(@"1--");    });    dispatch_sync(concurrentQueue, ^{        NSLog(@"2");        [NSThread sleepForTimeInterval:2];        NSLog(@"2--");    });    dispatch_sync(concurrentQueue, ^{        NSLog(@"3");        [NSThread sleepForTimeInterval:4];        NSLog(@"3--");    });    dispatch_sync(concurrentQueue, ^{        NSLog(@"4");        [NSThread sleepForTimeInterval:2];        NSLog(@"4--");    });}

dispatch_group

/* 串行队列：DISPATCH_QUEUE_SERIAL     开启一个子线程，按序执行 并行队列：DISPATCH_QUEUE_CONCURRENT 开启多个子线程，无序执行 */- (void)dispatch_group{    dispatch_queue_t queue = dispatch_queue_create("com.gcd.serialQueue", DISPATCH_QUEUE_SERIAL);    dispatch_group_t group = dispatch_group_create();    dispatch_group_async(group, queue, ^{        NSLog(@"1");        [NSThread sleepForTimeInterval:5];        NSLog(@"1--");    });    dispatch_group_async(group, queue, ^{        NSLog(@"2");        [NSThread sleepForTimeInterval:8];        NSLog(@"2--");    });    dispatch_group_async(group, queue, ^{        NSLog(@"3");        [NSThread sleepForTimeInterval:3];        NSLog(@"3--");    });    dispatch_group_notify(group, queue, ^{        NSLog(@"notify：任务都完成了");        dispatch_async(dispatch_get_main_queue(), ^{            NSLog(@"回到主线程");        });    });}

dispatch_group_enter和dispatch_group_leave是成对出现的，可以按照引用计数+1、-1理解。

/* 串行队列：DISPATCH_QUEUE_SERIAL     开启一个子线程，按序执行 并行队列：DISPATCH_QUEUE_CONCURRENT 开启多个子线程，无序执行 注意：dispatch_group_notify会与耗时最长的线程在同一个线程 */- (void)dispatch_group_enter{    dispatch_queue_t queue = dispatch_queue_create("com.GCD.group", DISPATCH_QUEUE_CONCURRENT);    dispatch_group_t group = dispatch_group_create();    dispatch_group_enter(group);    dispatch_async(queue, ^{        sleep(5);        NSLog(@"任务一完成");        dispatch_group_leave(group);    });    dispatch_group_enter(group);    dispatch_async(queue, ^{        sleep(8);        NSLog(@"任务二完成");        dispatch_group_leave(group);    });    dispatch_group_enter(group);    dispatch_async(queue, ^{        sleep(3);        NSLog(@"任务三完成");        dispatch_group_leave(group);    });    dispatch_group_notify(group, queue, ^{        NSLog(@"任务完成");        dispatch_async(dispatch_get_main_queue(), ^{            NSLog(@"回到主线程");        });    });}

dispatch_barrier

/* dispatch_barrier_sync和dispatch_barrier_async的共同点： 1、都会等待在它前面插入队列的任务（1、2、3）先执行完 2、都会等待他们自己的任务（0）执行完再执行后面的任务（4、5、6） dispatch_barrier_sync和dispatch_barrier_async的不共同点： 在将任务插入到queue的时候，dispatch_barrier_sync需要等待自己的任务（0）结束之后才会继续程序，然后插入被写在它后面的任务（4、5、6），然后执行后面的任务 而dispatch_barrier_async将自己的任务（0）插入到queue之后，不会等待自己的任务结束，它会继续把后面的任务（4、5、6）插入到queue */- (void)dispatch_barrier{    dispatch_queue_t queue = dispatch_queue_create("com.GCD.barrier", DISPATCH_QUEUE_CONCURRENT);    dispatch_async(queue, ^{        NSLog(@"1");        [NSThread sleepForTimeInterval:3];        NSLog(@"1--");    });    dispatch_async(queue, ^{        NSLog(@"2");        [NSThread sleepForTimeInterval:5];        NSLog(@"2--");    });    dispatch_async(queue, ^{        NSLog(@"3");        [NSThread sleepForTimeInterval:2];        NSLog(@"3--");    });    dispatch_barrier_async(queue, ^{        NSLog(@"barrier");        [NSThread sleepForTimeInterval:2];        NSLog(@"barrier--");        [NSThread sleepForTimeInterval:3];        NSLog(@"barrier==");    });    NSLog(@"aaa");    dispatch_async(queue, ^{        NSLog(@"4");        [NSThread sleepForTimeInterval:3];        NSLog(@"4--");    });    NSLog(@"bbb");    dispatch_async(queue, ^{        NSLog(@"5");        [NSThread sleepForTimeInterval:5];        NSLog(@"5--");    });    dispatch_async(queue, ^{        NSLog(@"6");        [NSThread sleepForTimeInterval:2];        NSLog(@"6--");    });}

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