NSOperation

NSOperation基本使用

• NSOperation基于GCD的面向对象的封装
• NSOperation配合NSOperationQueue也能实现多线程编程
  • 先将需要执行的操作封装到NSOperation中
  • 然后将NSOperation添加到NSOperationQueue中
  • 系统会自动将NSOperationQueue中的 NSOperation取出来
  • 将NSOperation中的操作自动放到一条线程中去执行

NSOperation是个抽象类没有封装操作的能力，一般都是用它的子类去封装需要执行的操作

代码

  NSInvocationOperation * op = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(run) object:nil];
    
 //执行操作
 [op start];

- (void)run
{
    //当前线程为主线程 因为op没有加到队列里面
    NSLog(@"%@",[NSThread currentThread]);
}


    NSBlockOperation * op = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"1---%@",[NSThread currentThread]);//主线程
    }];
    
    //添加额外任务(在子线程中执行)
    [op addExecutionBlock:^{
        NSLog(@"2---%@",[NSThread currentThread]);
    }];
    
    [op addExecutionBlock:^{
        NSLog(@"3---%@",[NSThread currentThread]);
    }];
    
    [op start];

NSOperationQueue

队列类型

• 主队列：[NSOperationQueue mainQueue];
• 其他队列：[[NSOperationQueue alloc]init];（包含串行和并发功能）
  • 添加到队列中的任务会自动放到子线程

GCD队列类型

• 并发队列：全局队列、自己创建的
• 串行队列：主队列、自己创建的

代码

    //创建队列  并发队列
    NSOperationQueue * queue = [[NSOperationQueue alloc]init];
    //设置最大并发数  如果是1就是串行队列
    queue.maxConcurrentOperationCount = 3;
    suspended = YES；//线程挂起 为NO时回复队列 继续执行
    [queue cancelAllOperations];//取消所有线程的执行 相当调用所有线程的cancel方法
#注意：如果是线程正在执行中你暂停线程或者取消线程时 当前线程是不会暂停的 会执行完毕当前线程后才会停止后面的线程
#注意：如果是自定义NSOperation  要不断的判断外面有没有取消你
#建议：执行完一段操作判断一下时候取消了线程

    //创建操作任务
    NSInvocationOperation * op1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(downLoad1) object:nil];
    NSInvocationOperation * op2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(downLoad2) object:nil];
    
    NSBlockOperation * op3 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"downLoad3--%@",[NSThread currentThread]);
    }];
    
    [op3 addExecutionBlock:^{
        NSLog(@"downLoad1--%@",[NSThread currentThread]);
    }];
    
    [op3 addExecutionBlock:^{
        NSLog(@"downLoad1--%@",[NSThread currentThread]);
    }];
    
    //添加操作到队列中
    [queue addOperation:op1];//只要添加到队列中 会自动开启线程
    [queue addOperation:op2];
    [queue addOperation:op3];

线程的依赖和监听

NSOperationQueue * queue = [[NSOperationQueue alloc]init];
    
    NSBlockOperation * op1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"download1 -- %@",[NSThread currentThread]);
    }];
    NSBlockOperation * op2 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"download2 -- %@",[NSThread currentThread]);
    }];
    NSBlockOperation * op3 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"download3 -- %@",[NSThread currentThread]);
    }];
    NSBlockOperation * op4 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"download4 -- %@",[NSThread currentThread]);
    }];
    op4.completionBlock = ^{
        
        NSLog(@"download4 执行完毕-- %@",[NSThread currentThread]);
        
    };
    
    //设置依赖(可以保证线程执行的顺序)
    [op3 addDependency:op1];//op3在op1之后执行
    [op3 addDependency:op2];//op3在op2之后执行
    
//    [op1 addDependency:op3];//不可以循环依赖
    
    [queue addOperation:op1];
    [queue addOperation:op2];
    [queue addOperation:op3];

线程之间的通讯

NSOperationQueue * queue = [[NSOperationQueue alloc]init];
    [queue addOperationWithBlock:^{
       
        NSURL * url = [NSURL URLWithString:@"http://h.hiphotos.baidu.com/image/h%3D200/sign=ea111e09952397ddc9799f046983b216/dc54564e9258d1093cf78e5cd558ccbf6d814dc3.jpg"];
        NSData * data = [NSData dataWithContentsOfURL:url];
        UIImage * image = [UIImage imageWithData:data];
        
        
        //回到主线程 刷新UI
        [[NSOperationQueue mainQueue]addOperationWithBlock:^{
          
            self.imageView.image = image;
            
        }];
        
    }];

###下载两张图片

NSOperationQueue * queue = [[NSOperationQueue alloc]init];
    
    //下载图片1
    __block UIImage * image1 = nil;
    NSBlockOperation * download1 = [NSBlockOperation blockOperationWithBlock:^{
        NSURL * url = [NSURL URLWithString:@"http://e.hiphotos.baidu.com/image/pic/item/8cb1cb1349540923592e4e479758d109b3de4947.jpg"];
        NSData * data = [NSData dataWithContentsOfURL:url];
        image1 = [UIImage imageWithData:data];
    }];
    
    //下载图片2
    __block UIImage * image2 = nil;
    NSBlockOperation * download2 = [NSBlockOperation blockOperationWithBlock:^{
        NSURL * url = [NSURL URLWithString:@"http://a.hiphotos.baidu.com/image/pic/item/f9dcd100baa1cd11daf25f19bc12c8fcc3ce2d46.jpg"];
        NSData * data = [NSData dataWithContentsOfURL:url];
        image2 = [UIImage imageWithData:data];
    }];
    
    //合成图片
    NSBlockOperation * combine = [NSBlockOperation blockOperationWithBlock:^{
       
        UIGraphicsBeginImageContext(CGSizeMake(350, 400));
        
        //绘制图片
        [image1 drawInRect:CGRectMake(0, 0, 175, 400)];
        image1 = nil;
        [image2 drawInRect:CGRectMake(175, 0, 175, 400)];
        image2 = nil;
        
        UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
        
        UIGraphicsEndImageContext();
        
        //回到主线程
        [[NSOperationQueue mainQueue]addOperationWithBlock:^{
            
            self.imageView.image = image;
            
        }];
    }];
    
    //设置依赖
    [combine addDependency:download1];
    [combine addDependency:download2];
    
    [queue addOperation:download1];
    [queue addOperation:download2];
    [queue addOperation:combine];