GCD调度组

GCD 调度组-oc

• 调度组是最重要的一监听一组任务的完成
  • 创建调度组
  • 创建队列
  • 调度组监听队列调度任务

```
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t que = dispatch_get_global_queue(0, 0);
dispatch_async(que, ^{
    NSLog(@"aaaaa%@",[NSThread currentThread]);
});
dispatch_async(que, ^{
    NSLog(@"bbbbb%@",[NSThread currentThread]);
});
dispatch_async(que, ^{
    NSLog(@"ccccccc%@",[NSThread currentThread]);
});
dispatch_group_notify(group, que, ^{
    NSLog(@"come herer%@",[NSThread currentThread]);
});

```
<!--{% asset_img GCD调度组1.png   %}-->

![](https://p1-jj.byteimg.com/tos-cn-i-t2oaga2asx/gold-user-assets/2018/9/5/165a8c79ae6972b1~tplv-t2oaga2asx-image.image)

• 调度的入组出组

• 入组，出组，相互对应，不多不少。

  dispatch_group_t group = dispatch_group_create();
  
  dispatch_queue_t que = dispatch_get_global_queue(0, 0);
  
  dispatch_group_enter(group);  // 入组
  
  dispatch_async(que, ^{
      NSLog(@"aaaaa%@",[NSThread currentThread]);
      dispatch_group_leave(group); // 出组
  });
  dispatch_group_enter(group);
  
  dispatch_async(que, ^{
      NSLog(@"bbbbb%@",[NSThread currentThread]);
      dispatch_group_leave(group);
  });
  dispatch_group_enter(group);
  
  dispatch_async(que, ^{
      NSLog(@"ccccccc%@",[NSThread currentThread]);
      dispatch_group_leave(group);
  });
  
  dispatch_group_notify(group, que, ^{
      NSLog(@"come herer%@",[NSThread currentThread]);
  });
  

  

GCD 调度组-swift

• 为了监听所有图像缓存，使用DispatchGroup

• enter 之后跟随block

• block 中有leave，配对存在

  func textGroup(){
      let group = DispatchGroup()
      let queue = DispatchQueue.global()
      group.enter()
      queue.async {
          print("aaaaa\(Thread.current)")
          group.leave()
      }
      group.enter()
      queue.async {
          print("bbbbb\(Thread.current)")
          group.leave()
      }
      group.notify(queue: DispatchQueue.main) {
          print("come here is end \(Thread.current)")
      } 
  }