NSOperation线程间通信

线程间的通信就是添加操作依赖

具体看下面的列子

• 1先创建queue,
• 2创建operation
• 3添加操作依赖,依赖的顺序,就是线程之间执行的顺序
• 4向queue里添加operation

//1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    
    __block UIImage *image1;
    __block UIImage *image2;
    //2 封装操作,下载图片1
    NSBlockOperation *download1 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSURL *url = [NSURL URLWithString:@"http://s15.sinaimg.cn/bmiddle/4c0b78455061c1b7f1d0e"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        image1 = [UIImage imageWithData:imageData];
        
        NSLog(@"download---%@",[NSThread currentThread]);
        
    }];
    
    //3 封装操作,下载图片2
    NSBlockOperation *download2 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSURL *url = [NSURL URLWithString:@"http://www.027art.com/feizhuliu/UploadFiles_6650/201109/2011091718442835.jpg"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        image2 = [UIImage imageWithData:imageData];
        
        NSLog(@"download---%@",[NSThread currentThread]);
        
    }];
    
    //4.封装合并图片的操作
    NSBlockOperation *combie = [NSBlockOperation blockOperationWithBlock:^{
        //4.1 开上下文
        UIGraphicsBeginImageContext(CGSizeMake(200, 200));
        
        //4.2 画图1
        [image1 drawInRect:CGRectMake(0, 0, 100, 200)];
        
        //4.3 画图2
        [image2 drawInRect:CGRectMake(100, 0, 100, 200)];
        
        //4.4 根据上下文得到图片
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        
        //4.5 关闭上下文
        UIGraphicsEndImageContext();
        
        //7.更新UI
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            self.imageView.image = image;
            NSLog(@"UI----%@",[NSThread currentThread]);
        }];
        
    }];
    
    //5.设置依赖关系
    [combie addDependency:download1];
    [combie addDependency:download2];
    
    //6.添加操作到队列中
    [queue addOperation:download2];
    [queue addOperation:download1];
    [queue addOperation:combie];