NSOperation

相比GCD NSOperation更加的灵活

1.NSInvocationOperation

创建操作 ---> 创建队列 ---> 操作加入队列

    // 处理事务
    NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(handleInvocation:) object:@"hello"];

    //如果没有创建队列直接启动事务就在主线程里
    //[op start];

    // 创建队列
    NSOperationQueue *queue   = [[NSOperationQueue alloc] init];
    // 操作加入队列
    [queue addOperation:op];
    
    //在这里不可以启动，因为已经启动，此时在去启动就会把一个在running状态的队列重新start 造成线程混乱直接GG  
    //可以用 [[NSOperationQueue mainQueue] addOperation:op];
    //[op start];

2.NSBlockOperation

相比NSInvocationOperation，NSBlockOperation是函数式编程，代码可读性更强

    //1:创建blockOperation
    NSBlockOperation *bo = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"%@",[NSThread currentThread]);
        sleep(3);
    }];
    
    //1.1 添加执行代码块
    [bo addExecutionBlock:^{
        NSLog(@"这是一个执行代码块 - %@",[NSThread currentThread]);
    }];
    //1.2 设置监听
    bo.completionBlock = ^{
        NSLog(@"完成了!!!");
    };
    
    //2:创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    //3:添加到队列
    [queue addOperation:bo];
    NSLog(@"事务添加进了NSOperationQueue");

3.优先级

- (void)demo{
    // 优先级
    NSBlockOperation *bo1 = [NSBlockOperation blockOperationWithBlock:^{
        for (int i = 0; i < 10; i++) {
            NSLog(@"**第一个操作** %d --- %@", i, [NSThread currentThread]);
        }
    }];
    // 设置优先级 - 最高
    bo1.qualityOfService = NSQualityOfServiceUserInteractive;
    
    //创建第二个操作
    NSBlockOperation *bo2 = [NSBlockOperation blockOperationWithBlock:^{
        for (int i = 0; i < 10; i++) {
            NSLog(@"第二个操作 %d --- %@", i, [NSThread currentThread]);
        }
    }];
    // 设置优先级 - 最低
    bo2.qualityOfService = NSQualityOfServiceBackground;
    
    //2:创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    //3:添加到队列
    [queue addOperation:bo1];
    [queue addOperation:bo2];
    
}

4.线程通讯

- (void)demo {
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    queue.name = @"hello";
    [queue addOperationWithBlock:^{
        NSLog(@"%@ = %@",[NSOperationQueue currentQueue],[NSThread currentThread]);
        //模拟请求网络
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            NSLog(@"%@ --%@",[NSOperationQueue currentQueue],[NSThread currentThread]);
        }];
    }];
}

5.控制并发量

- (void)demo {
    // 设置并发数
    self.queue.name = @"hello";
    self.queue.maxConcurrentOperationCount = 2;
    for (int i = 0; i<10; i++) {
        [self.queue addOperationWithBlock:^{ // 一个任务
            [NSThread sleepForTimeInterval:2];
            NSLog(@"%d-%@",i,[NSThread currentThread]);
        }];
    }
}

6.依赖关系

- (void)demo{
    NSBlockOperation *bo1 = [NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:0.5];
        NSLog(@"请求token");
    }];
    
    NSBlockOperation *bo2 = [NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:0.5];
        NSLog(@"拿着token,请求数据1");
    }];
    
    NSBlockOperation *bo3 = [NSBlockOperation blockOperationWithBlock:^{
        [NSThread sleepForTimeInterval:0.5];
        NSLog(@"拿着数据1,请求数据2");
    }];
    
    // 建立依赖最容易犯的问题就是循环嵌套
    [bo2 addDependency:bo1];
    [bo3 addDependency:bo2];
    
    //[bo1 addDependency:bo3];

    [self.queue addOperations:@[bo1,bo2,bo3] waitUntilFinished:YES];
    
    NSLog(@"执行完了?我要干其他事");
}

7.挂起、继续、取消

正在执行的操作无法挂起或者取消
执行结果发现,正在执行的操作无法取消,因为这要回想到之前的NSThread
只有在内部判断才能取消完毕