多线程CGD调度组原理

我们常用的GCD调度组方式

//GCD常用调度组写法
-(void)demo1{
    
    //创建调度组和队列
    dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("ChangYong", DISPATCH_QUEUE_CONCURRENT);
    
    //将任务添加到调度组
    dispatch_group_async(group, queue, ^{
        NSLog(@"耗时操作_11111111");
    });
    dispatch_group_async(group, queue, ^{
        //模拟耗时操作
        [NSThread sleepForTimeInterval:2];
        NSLog(@"耗时操作_22222222");
    });
    dispatch_group_async(group, queue, ^{
        NSLog(@"耗时操作_33333333");
    });
    
    //所有任务执行完毕后执行的任务
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"所有任务执行完毕, 更新UI操作");
    });
}

GCD调度组原理

//GCD调度组原理方法
-(void)demo2{
    
    //创建调度组和队列
    dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("YuanLi", DISPATCH_QUEUE_CONCURRENT);
    
    //任务1
    dispatch_group_enter(group);
    dispatch_async(queue, ^{
        NSLog(@"任务1");
        dispatch_group_leave(group);
    });
    
    //任务2
    dispatch_group_enter(group);
    dispatch_async(queue, ^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"任务2");
        dispatch_group_leave(group);
    });
    
    //任务3
    dispatch_group_enter(group);
    dispatch_async(queue, ^{
        NSLog(@"任务3");
        dispatch_group_leave(group);
    });
    
    //任务全部执行完毕
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
       
        NSLog(@"任务执行完毕, 刷新UI");
    });
    
    //等待上面代码执行完毕后在执行下面的代码, 参数2:等待超时时间
    //dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
    
    NSLog(@"Hello");
}