iOS GCD(6)

//这里指定等待时间1s，即1s后查看dispatch group中的处理是否全部执行结束
    dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, 1ull*NSEC_PER_SEC);
    long result = dispatch_group_wait(group, time);
    if (result == 0) {
        //属于dispatch group中的全部处理都执行结束
    }
    else {
        //属于dispatch group的某一个处理还在执行
    }

[cpp]
//这里也可以指定DISPATCH_TIME_NOW,则不用任何等待即可判断属于dispatch group中的处理是否全部执行结束  
   long result = dispatch_group_wait(group, DISPATCH_TIME_NOW); 

 //这里也可以指定DISPATCH_TIME_NOW,则不用任何等待即可判断属于dispatch group中的处理是否全部执行结束
    long result = dispatch_group_wait(group, DISPATCH_TIME_NOW);

 6、dispatch_barrier_async

[cpp]
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0); 
     
    dispatch_async(queue, ^{ 
        //表示执行数据读取任务  
        NSLog(@"blk1_reading"); 
    }); 
    dispatch_async(queue, ^{ 
        NSLog(@"blk2_reading"); 
    }); 
     
    dispatch_async(queue, ^{ 
        //表示执行数据写入处理任务  
        NSLog(@"blk1_writting"); 
    }); 
     
    dispatch_async(queue, ^{ 
        NSLog(@"blk3_reading"); 
    }); 
    dispatch_async(queue, ^{ 
        NSLog(@"blk4_reading"); 
    }); 

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
   
    dispatch_async(queue, ^{
        //表示执行数据读取任务
        NSLog(@"blk1_reading");
    });
    dispatch_async(queue, ^{
        NSLog(@"blk2_reading");
    });
   
    dispatch_async(queue, ^{
        //表示执行数据写入处理任务
        NSLog(@"blk1_writting");