NSOperation简单使用2

「这是我参与2022首次更文挑战的第5天，活动详情查看：2022首次更文挑战」。

使用NSOperationQueue时，设置maxConcurrentOperationCount最大并发数，默认-1并行，1即为串行。

• addOperationWithBlock

NSLog(@"---begin");
    //队列
    NSOperationQueue *queue=[[NSOperationQueue alloc]init];
    //任务
    [queue addOperationWithBlock:^{
        [self test];
    }];
    [queue addOperationWithBlock:^{
        [NSThread sleepForTimeInterval:2];
        for (int i=3; i<6; i++) {
            NSLog(@"---%d---%@",i,[NSThread currentThread]);
        }
    }];
    NSLog(@"---end");

效果一样，使用方法不一样而已。

• 添加依赖和监听addDependency,completionBlock

NSLog(@"---begin");
    NSOperationQueue *queue=[[NSOperationQueue alloc]init];
    NSBlockOperation *blockOp=[NSBlockOperation blockOperationWithBlock:^{
        for (int i=0; i<3; i++) {
            NSLog(@"---%d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp1=[NSBlockOperation blockOperationWithBlock:^{
        for (int i=3; i<6; i++) {
            NSLog(@"---%d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp2=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:2];
        for (int i=6; i<9; i++) {
            NSLog(@"---%d---%@",i,[NSThread currentThread]);
        }
    }];
    //blockOp 依赖于blockOp1，即等blockOp1 执行完再执行 blockOp
    [blockOp addDependency:blockOp1];
    
    [queue addOperation:blockOp];
    [queue addOperation:blockOp1];
    [queue addOperation:blockOp2];
    blockOp.completionBlock=^{
        NSLog(@"---blockOp  over");
    };
    NSLog(@"---end");

编译结果如下：

blockOp 依赖于blockOp1,等blockOp1里的任务执行完再执行blockOp的任务，blockOp执行完completionBlock回调打印---blockOp over. blockOp1和blockOp2执行顺序先后是不确定的(异步)。

• NSOperationQueue的取消

-(void)demo6
{
    NSLog(@"---h begin");
    NSOperationQueue *queue=[[NSOperationQueue alloc]init];
    queue.maxConcurrentOperationCount=1;
    NSBlockOperation *blockOp=[NSBlockOperation blockOperationWithBlock:^{
        
        for (int i=0; i<3; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp1=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:1];
        for (int i=3; i<6; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp2=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:3];
        for (int i=6; i<9; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp3=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:4];
        for (int i=9; i<12; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    
    [queue addOperation:blockOp];
    [queue addOperation:blockOp1];
    [queue addOperation:blockOp2];
    [queue addOperation:blockOp3];
    self.blockOperation=blockOp3;
    self.queue=queue;
    NSLog(@"---h end");
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    //[self.blockOperation cancel];
    [self.queue cancelAllOperations];
}

编译结果如下：

• NSOperationQueue的暂停恢复

-(void)demo6
{
    NSLog(@"---h begin");
    NSOperationQueue *queue=[[NSOperationQueue alloc]init];
    queue.maxConcurrentOperationCount=1;
    NSBlockOperation *blockOp=[NSBlockOperation blockOperationWithBlock:^{
        
        for (int i=0; i<3; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp1=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:1];
        for (int i=3; i<6; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp2=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:3];
        for (int i=6; i<9; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    NSBlockOperation *blockOp3=[NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:4];
        for (int i=9; i<12; i++) {
            NSLog(@"---h %d---%@",i,[NSThread currentThread]);
        }
    }];
    
    [queue addOperation:blockOp];
    [queue addOperation:blockOp1];
    [queue addOperation:blockOp2];
    [queue addOperation:blockOp3];
    self.blockOperation=blockOp3;
    self.queue=queue;
    NSLog(@"---h end");
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    self.queue.suspended=!self.queue.suspended;
    if (self.queue.suspended) {
        NSLog(@"---h暂停");
    }else
    {
        NSLog(@"---h恢复");
    }
}

编译结果如下：

 ![NSOperationQueue的暂停恢复.png](http://upload-images.jianshu.io/upload_images/3339381-4b450b2aad3becbf.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

NSOperationQueue有个suspended属性，当为YES的时候暂停，为NO时执行。当我点击屏幕时打印暂停，打印结果可以看出并没有马上暂停，它会把正在执行的任务完成才暂停。