NSOperation操作依赖和监听

1.操作依赖

　　NSOperation之间可以设置依赖来保证执行顺序

　　比如一定要让操作A执行完后，才能执行操作B，可以这么写

　　[operationB addDependency:operationA]; // 操作B依赖于操作A

　　可以在不同queue的NSOperation之间创建依赖关系

　　

　　注意：不能相互依赖

　　比如A依赖B，B依赖A

 -(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
     //1.创建队列
     NSOperationQueue *queue = [[NSOperationQueue alloc]init];
     NSOperationQueue *queue1 = [[NSOperationQueue alloc]init];
     //2.封装操作
     NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"1----%@",[NSThread currentThread]);

     }];
     NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"2----%@",[NSThread currentThread]);

     }];
     NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"3----%@",[NSThread currentThread]);

     }];
     NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"4----%@",[NSThread currentThread]);

     }];
     NSBlockOperation *op5 = [NSBlockOperation blockOperationWithBlock:^{
         for (NSInteger i=; i<; i++) {
             NSLog(@"5-%zd---%@",i,[NSThread currentThread]);
         }

     }];

     //添加操作依赖,注意不能循环依赖
     [op1 addDependency:op5];
     [op1 addDependency:op4];

     //添加操作到队列
     [queue addOperation:op1];
     [queue addOperation:op2];
     [queue addOperation:op3];
     [queue addOperation:op4];
     [queue1 addOperation:op5];
 }

示例

2.操作的监听

　　可以监听一个操作的执行完毕

　　- (void (^)(void))completionBlock;

　　- (void)setCompletionBlock:(void (^)(void))block;

 -(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
     //1.创建队列
     NSOperationQueue *queue = [[NSOperationQueue alloc]init];

     //2.封装操作

     NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"4----%@",[NSThread currentThread]);

     }];
     NSBlockOperation *op5 = [NSBlockOperation blockOperationWithBlock:^{
         for (NSInteger i=; i<; i++) {
             NSLog(@"5-%zd---%@",i,[NSThread currentThread]);
         }

     }];

 //操作监听
     op4.completionBlock = ^{
         NSLog(@"op4已经完成了---%@",[NSThread currentThread]);
     };

     [queue addOperation:op4];
     [queue addOperation:op5];
 }

示例