Cocoa operation的创建及简单实用

创建方法

    
    //方法一：操作队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    
    //最大操作数：设为1的话，从前往后执行；设置为其他，并发执行
    queue.maxConcurrentOperationCount = 1;
    
    //被挂起（暂停）目的是：加载了所有的任务才执行队列
    queue.suspended = YES;
    
    [queue addOperationWithBlock:^{
        
        NSLog(@"1--是否为主线程：%d",[[NSThread currentThread]isMainThread]);
        NSLog(@"1--优先级:%f",[NSThread threadPriority]);
        
        
    }];
    

    //方法二：NSOperation（操作任务）的子类: NSInvocationOperation
    NSInvocationOperation *invocationOp = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationAction:) object:@"invocation"];
  
    //添加到队列中
    [queue addOperation:invocationOp];
    
    //监听invocationOp任务是否完成，完成后调用此方法
    invocationOp.completionBlock = ^(){
        
        NSLog(@"2--invocationOp任务完成");
    };

    //NSInvocationOperation线程实现的方法
    - (void)invocationAction:(NSString *)t{
    
    NSLog(@"2--%@",t);
    
    NSLog(@"2--是否为主线程：%d",[[NSThread currentThread]isMainThread]);
    NSLog(@"2--优先级:%f",[NSThread threadPriority]);
  }

    
    
    //方法三：NSOperation（操作任务）的子类:NSBlockOperation可以并发执行一个或多个任务
    NSBlockOperation *blockOp = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"3---是否为主线程：%d",[[NSThread currentThread]isMainThread]);
        NSLog(@"3--优先级:%f",[NSThread threadPriority]);
        
    }];
    
    [blockOp addExecutionBlock:^{
        
        NSLog(@"3--再执行一个任务");
    }];
    
    [blockOp addExecutionBlock:^{
        
        NSLog(@"3--又执行一个任务");
    }];
    
    //该方法监听blockOp任务是否完成，完成后调用此方法
    blockOp.completionBlock = ^(){
        
        NSLog(@"3--blocp执行完成");
        
    };
    
    [queue addOperation:blockOp];
    
    //添加依赖关系：意思是先执行blockOp，再执行invocationOp
    [invocationOp addDependency:blockOp];

    
    
    //方法四：自定义opration
    CustomOpration *customOpration = [[CustomOpration alloc]init];
    //设置优先级:来改变任务处理的顺序，这里设置为最高等级，最先处理
    customOpration.queuePriority = NSOperationQueuePriorityVeryHigh;
    [queue addOperation:customOpration];


  //自定义CustomOpration.m 文件中的代码
  
  #import "CustomOpration.h"

  @implementation CustomOpration

  - (void)main{
    
    for (int i=0; i<5; i++) {
        NSLog(@"4------%d",i);
      }
  }

取消方法

    
    
    
    
    //取消某个任务 ，这里的cancelOp已经设为全局，目的为了后面方便使用
    cancelOp = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(cancelOpAction) object:nil];
    
    [self performSelector:@selector(cancelSingle:) withObject:cancelOp afterDelay:1];

    [queue addOperation:cancelOp];
    
    //取消所有队列，不过只能取消没有执行的队列
    //[queue cancelAllOperations];
    
    
    //取消操作队列暂停
    queue.suspended = NO;
}

//取消的方法
- (void)cancelSingle:(NSInvocationOperation *)op{
    
    [op cancel];
}

//cancelOp线程实现的方法
- (void)cancelOpAction{
    
    //休眠2秒
    [NSThread sleepForTimeInterval:2];
    
    if ([cancelOp isCancelled]) {
        //如果确定已经取消，打印下面的语句，其他语句不打印
        NSLog(@"已经取消了，不会执行以下语句");
    }
    
    NSLog(@"我能执行吗");
    
}