iOS 多线程(NSOperationQueue)

//1.创建操作对象,封装需要执行的任务
    NSInvocationOperation * operation =[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download) object:nil];
    
    //2.执行操作(默认情况下,如果操作没有放到队列queue中,都是同步执行)
    [operation start];

- (void)download{
    NSLog(@"--------下载图片-----%@",[NSThread currentThread]);
}

 //1.封装操作
    NSBlockOperation * operation=[NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"--------下载图片-----%@",[NSThread currentThread]);
    }];
    
    [operation addExecutionBlock:^{
         NSLog(@"--------下载图片1-----%@",[NSThread currentThread]);
    }];
    [operation addExecutionBlock:^{
         NSLog(@"--------下载图片2-----%@",[NSThread currentThread]);
    }];
    

    //2.执行操作
    [operation start];
    
    //注意:只要NSBlockOperation封装的操作数>1,就会异步执行操作

 //创建操作队列
    NSOperationQueue * queue =[[NSOperationQueue alloc]init];
    NSInvocationOperation *operation1 =[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download) object:nil];
    NSInvocationOperation * operation2 =[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(run) object:nil];
    
    NSBlockOperation * operation3 =[NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"--------下载图片2-----%@",[NSThread currentThread]);
        
    }];
    
    [operation3 addExecutionBlock:^{
        NSLog(@"--------run2-----%@",[NSThread currentThread]);

    }];
    
    
    [queue addOperation:operation1];
    [queue addOperation:operation2];
    [queue addOperation:operation3];
 //将操作放在队列里才能异步操作