刀哥多线程之调度组gcd-12-group

调度组

常规用法

- (void)group1 {

    // 1. 调度组

    dispatch_group_t group = dispatch_group_create();

    // 2. 队列

    dispatch_queue_t q = dispatch_get_global_queue(0, 0);

    // 3. 将任务添加到队列和调度组

    dispatch_group_async(group, q, ^{

        [NSThread sleepForTimeInterval:1.0];

        NSLog(@"任务 1 %@", [NSThread currentThread]);

    });

    dispatch_group_async(group, q, ^{

        NSLog(@"任务 2 %@", [NSThread currentThread]);

    });

    dispatch_group_async(group, q, ^{

        NSLog(@"任务 3 %@", [NSThread currentThread]);

    });

    // 4. 监听所有任务完成

    dispatch_group_notify(group, q, ^{

        NSLog(@"OVER %@", [NSThread currentThread]);

    });

    // 5. 判断异步

    NSLog(@"come here");

}

enter & leavel

// MARK: - 调度组 2

- (void)group2 {

    // 1. 调度组

    dispatch_group_t group = dispatch_group_create();

    // 2. 队列

    dispatch_queue_t q = dispatch_get_global_queue(0, 0);

    // dispatch_group_enter & dispatch_group_leave 必须成对出现

    dispatch_group_enter(group);

    dispatch_group_async(group, q, ^{

        NSLog(@"任务 1 %@", [NSThread currentThread]);

        // dispatch_group_leave 必须是 block 的最后一句

        dispatch_group_leave(group);

    });

    dispatch_group_enter(group);

    dispatch_group_async(group, q, ^{

        NSLog(@"任务 2 %@", [NSThread currentThread]);

        // dispatch_group_leave 必须是 block 的最后一句

        dispatch_group_leave(group);

    });

    // 4. 阻塞式等待调度组中所有任务执行完毕

    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);

    // 5. 判断异步

    NSLog(@"OVER %@", [NSThread currentThread]);

}