GCD 高级用法总结

延时执行三种方法 并行/串行/主队列综合练习 队列组

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{   
    [selfdemo];
}

//延时执行
-(void)demo{
    //方法1 timer
//    NSTimer *timer = [NSTimer timerWithTimeInterval:1 target:self selector:@selector(task) userInfo:nil repeats:YES];
//    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
    
    //方法2
    [selfperformSelector:@selector(task)withObject:nilafterDelay:3];
    
    //方法3
    /*参数1：延时时间  dispatch_time生成时间 纳秒为计时单位 精度高
     *参数2：队列
     *参数3：任务
     *异步执行       */
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1*NSEC_PER_SEC)),dispatch_get_main_queue(), ^{
        NSLog(@"task");
    });
    NSLog(@"over");
}

-(void)task{
    NSLog(@"task");
}

//模拟下载任务
/*1、下载 L01.zip
 *2、下载 L02.zip
 *3、通知UI：下载完成
 1、2在3之前执行
 */
-(void)demo1{
    //串行，异步顺序下载
    dispatch_queue_t serialQueue =dispatch_queue_create("serialQueue",DISPATCH_QUEUE_SERIAL);
    
    dispatch_async(serialQueue, ^{
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//5秒内的随机时间
        dispatch_async(serialQueue, ^{
            NSLog(@"%@下载 L01.zip",[NSThreadcurrentThread]);
        });
    
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//5秒内的随机时间
        dispatch_async(serialQueue, ^{
            NSLog(@"%@下载 L02.zip",[NSThreadcurrentThread]);
        });
    
        dispatch_async(serialQueue, ^{
            dispatch_async(dispatch_get_main_queue(), ^{
                NSLog(@"%@下载完成",[NSThreadcurrentThread]);
            });
        });
    });
}

-(void)demo2{
    //并行异步   "shift+command+o"快速查找
    dispatch_queue_t concurrentQueue =dispatch_queue_create("concurrentQueue",DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(concurrentQueue, ^{
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//5秒内的随机时间
        //并行同步顺序下载
        dispatch_sync(concurrentQueue, ^{
             NSLog(@"%@下载 L01.zip",[NSThreadcurrentThread]);
        });
        
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//5秒内的随机时间
        dispatch_sync(concurrentQueue, ^{
            NSLog(@"%@下载 L02.zip",[NSThreadcurrentThread]);
        });
        
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"%@下载完成",[NSThreadcurrentThread]);
        });
    });
}

//任务1、2在子线程上先顺序执行后，任务3、4在主线程上执行，最后任务5、6、7在子线程上并发无序执行
-(void)demo3{
    dispatch_queue_t serialQueue =dispatch_queue_create("serialQueue",DISPATCH_QUEUE_SERIAL);
    dispatch_queue_t concurrentQueue =dispatch_queue_create("concurrentQueue",DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(concurrentQueue, ^{
        dispatch_sync(serialQueue, ^{
            NSLog(@"%@执行任务1",[NSThreadcurrentThread]);
        });
        
        dispatch_sync(serialQueue, ^{
            NSLog(@"%@执行任务2",[NSThreadcurrentThread]);
        });
        
        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"%@执行任务3",[NSThreadcurrentThread]);
        });

        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"%@执行任务4",[NSThreadcurrentThread]);
        });
        
        dispatch_async(concurrentQueue, ^{
            dispatch_async(concurrentQueue, ^{
                NSLog(@"%@执行任务5",[NSThreadcurrentThread]);
            });
            dispatch_async(concurrentQueue, ^{
                NSLog(@"%@执行任务6",[NSThreadcurrentThread]);
            });
            dispatch_async(concurrentQueue, ^{
                NSLog(@"%@执行任务7",[NSThreadcurrentThread]);
            });
        });
    });
}

//队列组
-(void)demo4{
    NSLog(@"begin");
    //创建队列组
    dispatch_group_t group =dispatch_group_create();
    
    //开启异步任务
    dispatch_group_async(group,dispatch_get_global_queue(0,0), ^{
        //模拟网络卡
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//休眠5秒内随机时间
        NSLog(@"%@下载 L01.zip",[NSThreadcurrentThread]);
    });
    
    dispatch_group_async(group,dispatch_get_global_queue(0,0), ^{
        //模拟网络卡
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//休眠5秒内随机时间
        NSLog(@"%@下载 L02.zip",[NSThreadcurrentThread]);
    });

    dispatch_group_notify(group,dispatch_get_global_queue(0,0), ^{
        NSLog(@"%@下载完成",[NSThreadcurrentThread]);
    });
}

-(void)demo5{
/*    dispatch_group_async(dispatch_group_t group, dispatch_queue_t queue, dispatch_block_t block)
    {
        dispatch_retain(group);
        dispatch_group_enter(group);
        dispatch_async(queue, ^{
            block();
            dispatch_group_leave(group);
            dispatch_release(group);
        });     */
    
    dispatch_group_t group =dispatch_group_create();
    
    dispatch_group_enter(group);
    dispatch_group_async(group,dispatch_get_global_queue(0,0), ^{
        //模拟网络卡
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//休眠5秒内随机时间
        NSLog(@"%@下载 L01.zip",[NSThreadcurrentThread]);
        dispatch_group_leave(group);
    });
    
    dispatch_group_enter(group);
    dispatch_group_async(group,dispatch_get_global_queue(0,0), ^{
        //模拟网络卡
        [NSThreadsleepForTimeInterval:arc4random_uniform(5)];//休眠5秒内随机时间
        NSLog(@"%@下载 L02.zip",[NSThreadcurrentThread]);
        dispatch_group_leave(group);
    });

    dispatch_group_notify(group,dispatch_get_global_queue(0,0), ^{
        NSLog(@"%@下载完成",[NSThreadcurrentThread]);
    });
}

两个网络请求同步问题

- (void)loadData {
    NSString *appIdKey = @"8781e4ef1c73ff20a180d3d7a42a8c04";
    NSString* urlString_1 = @"http://api.openweathermap.org/data/2.5/weather";
    NSString* urlString_2 = @"http://api.openweathermap.org/data/2.5/forecast/daily";
    NSDictionary* dictionary =@{@"lat":@"40.04991291",
                                @"lon":@"116.25626162",
                                @"APPID" : appIdKey};
    // 创建组
    dispatch_group_t group = dispatch_group_create();
    // 将第一个网络请求任务添加组中
    dispatch_group_async(group,  dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // 创建信号量
        dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
        // 开始网络请求任务
        AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
        [manager GET:urlString_1 parameters:dictionary progress:^(NSProgress * _Nonnull downloadProgress) {
            
        } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
            NSLog(@"成功请求数据1:%@",[responseObject class]);
            // 如果请求成功，发送信号量
            dispatch_semaphore_signal(semaphore);
        } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
            NSLog(@"失败请求数据");
            // 如果请求失败，也发送信号量
            dispatch_semaphore_signal(semaphore);
        }];
        // 在网络请求任务成功之前，信号量等待中
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    });
    
    // 将第二个网络请求任务添加到组中
    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // 创建信号量
        dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
        // 开始网络请求任务
        AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
        [manager GET:urlString_2
          parameters:dictionary
            progress:nil
             success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
                 NSLog(@"成功请求数据2:%@",[responseObject class]);
                 // 如果请求成功，发送信号量
                 dispatch_semaphore_signal(semaphore);
             } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
                 NSLog(@"失败请求数据");
                 // 如果请求失败，也发送信号量
                 dispatch_semaphore_signal(semaphore);
             }];
        // 在网络请求任务成功之前，信号量等待中
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    });
    dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSLog(@"完成了网络请求，不管网络请求失败了还是成功了。");
    });
}