NSOperationはシステムを使用してサブクラスを提供する方法--複雑なタスクを処理する

 //      

    NSOperationQueue *operation=[[NSOperationQueue alloc]init];

    //     NSBlockOperation  

    NSBlockOperation *myOperation=[NSBlockOperation blockOperationWithBlock:^{

        NSData *firstData=[NSData dataWithContentsOfURL:[NSURL URLWithString:KURL1]];

     

        dispatch_async(dispatch_get_main_queue(), ^{

           

            _firstImageView.image=[UIImage imageWithData:firstData];

       });

       

    }];

  

    //            

    [myOperation addExecutionBlock:^{

        NSData *secondData=[NSData dataWithContentsOfURL:[NSURL URLWithString:KURL1]];

        

        dispatch_async(dispatch_get_main_queue(), ^{

            

            _secondImageView.image=[UIImage imageWithData:secondData];

        });

        

    }];

    [operation addOperation:myOperation];