NSOperation && NSOperationQueue

NSOperation

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

1、NSInvocationOperation - 同步执行

/// 1、NSInvocationOperation - 同步执行
- (IBAction)createNSInvocationSynchronousExecution {
    
     // 创建操作
    NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    NSInvocationOperation *operation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    NSInvocationOperation *operation3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    
    // operation直接调用start，是同步执行（在当前线程执行操作）
    [operation1 start];
    [operation2 start];
    [operation3 start];
    
}

2、NSInvocationOperation - 异步执行

/// 2、NSInvocationOperation - 异步执行
- (IBAction)createNSInvocationOperationAsynchronousExecution {
    
    // 创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    // 创建操作
    NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    
    NSInvocationOperation *operation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    
    NSInvocationOperation *operation3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    
    // 添加操作到队列中，会自动异步执行
    [queue addOperation:operation1];
    [queue addOperation:operation2];
    [queue addOperation:operation3];
}

3、NSBlockOperation - 同步执行1

- (IBAction)createNSBlockOperationAsynchronousExecution1 {
    
    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{

        NSLog(@"---下载图片----1---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{

        NSLog(@"---下载图片----2---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{

        NSLog(@"---下载图片----3---%@", [NSThread currentThread]);
    }];
    
    [operation1 start];
    [operation2 start];
    [operation3 start];
    // 同步执行
}

4、NSBlockOperation - 同步执行2

/// 4、NSBlockOperation - 同步执行2
- (IBAction)createNSBlockOperationAsynchronousExecution2 {
    
    NSBlockOperation *operation = [[NSBlockOperation alloc] init];
    
    [operation addExecutionBlock:^{
        
        NSLog(@"---下载图片----1---%@", [NSThread currentThread]);
    }];
    
    [operation addExecutionBlock:^{
        
        NSLog(@"---下载图片----2---%@", [NSThread currentThread]);
    }];
    
    [operation addExecutionBlock:^{
        
        NSLog(@"---下载图片----3---%@", [NSThread currentThread]);
    }];
    
    [operation start];
    // 同步执行
}

5、创建队列 - 异步执行

/// 5、创建队列 - 异步执行
- (IBAction)createNSBlockOperationAsynchronousExecution3 {
    
    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----11---%@", [NSThread currentThread]);
    }];
    
    [operation1 addExecutionBlock:^{
        
        NSLog(@"---下载图片----12---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----2---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----3---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----4---%@", [NSThread currentThread]);
    }];
    
    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    // 2.添加操作到队列中（自动异步执行）
    [queue addOperation:operation1];
    [queue addOperation:operation2];
    [queue addOperation:operation3];
    [queue addOperation:operation4];
}

6、主队列 - 在主线程中同步执行

/// 6、主队列 - 在主线程中同步执行
- (IBAction)createNSBlockOperationAsynchronousExecution4 {
    
    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----11---%@", [NSThread currentThread]);
    }];
    
    [operation1 addExecutionBlock:^{
        
        NSLog(@"---下载图片----12---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----2---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----3---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
        
        NSLog(@"---下载图片----4---%@", [NSThread currentThread]);
    }];
    
    // 主队列
    NSOperationQueue *queue = [NSOperationQueue mainQueue];
    
    // 2.添加操作到队列中（自动同步执行）
    [queue addOperation:operation1];
    [queue addOperation:operation2];
    [queue addOperation:operation3];
    [queue addOperation:operation4];
}

如下图：

Simulator Screen Shot - iPhone 11 Pro Max - 2020-04-30 at 17.49.28.png

NSOperationQueue

1、设置依赖

/// 设置依赖
- (IBAction)dependencyOperation {
    
    /**
     假设有A、B、C、D四个操作，要求：
     1. 4个操作都异步执行
     2.操作D依赖于操作C
     3. 操作C依赖于操作B
     4. 操作B依赖于操作A
     */
    
    // 1.创建一个队列（非主队列）
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    // 2.创建4个操作
    NSBlockOperation *operationA = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"A-----%@", [NSThread currentThread]);
    }];
    
//    [operationA addExecutionBlock:^{
//
//        NSLog(@"A2---%@", [NSThread currentThread]);
//    }];
//
//    [operationA setCompletionBlock:^{
//
//        NSLog(@"AAAAA---%@", [NSThread currentThread]);
//    }];
    
    NSBlockOperation *operationB = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"B-----%@", [NSThread currentThread]);
    }];
    NSBlockOperation *operationC = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"C-----%@", [NSThread currentThread]);
    }];
    NSBlockOperation *operationD = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"D-----%@", [NSThread currentThread]);
    }];
    
    // 设置依赖
    [operationB addDependency:operationA];
    [operationC addDependency:operationB];
    [operationD addDependency:operationC];
    
    // 3.添加操作到队列中（自动异步执行任务）
    [queue addOperation:operationD];
    [queue addOperation:operationC];
    [queue addOperation:operationA];
    [queue addOperation:operationB];
}

2、设置最大并发

/// 设置最大并发
- (IBAction)setMaxOperationCount {
    
    // 添加操作到队列中（自动异步执行任务，并发）
    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下载图片1---%@", [NSThread currentThread]);
    }];
    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下载图片2---%@", [NSThread currentThread]);
    }];
    NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下载图片3---%@", [NSThread currentThread]);
    }];
    NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下载图片4---%@", [NSThread currentThread]);
    }];
    NSInvocationOperation *operation5 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
    
    [self.queue addOperation:operation1];
    [self.queue addOperation:operation2];
    [self.queue addOperation:operation3];
    [self.queue addOperation:operation4];
    [self.queue addOperation:operation5];
    
    [self.queue addOperationWithBlock:^{
        NSLog(@"下载图片5---%@", [NSThread currentThread]);
    }];
    [self.queue addOperationWithBlock:^{
        NSLog(@"下载图片6---%@", [NSThread currentThread]);
    }];
    [self.queue addOperationWithBlock:^{
        NSLog(@"下载图片7---%@", [NSThread currentThread]);
    }];
    [self.queue addOperationWithBlock:^{
        NSLog(@"下载图片8---%@", [NSThread currentThread]);
    }];
    [self.queue addOperationWithBlock:^{
        NSLog(@"下载图片9---%@", [NSThread currentThread]);
    }];
    
//    [queue cancelAllOperations];
}



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

- (void)didReceiveMemoryWarning {
    
    [super didReceiveMemoryWarning];
    
    [self.queue cancelAllOperations]; // 取消队列中的所有任务（不可恢复）
}

#pragma mark- scrollViewDelegate

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    
    [self.queue setSuspended:YES]; // 暂停队列中的所有任务
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    
    [self.queue setSuspended:NO]; // 恢复队列中的所有任务
}

#pragma mark- lazying

- (NSOperationQueue *)queue {
    if (!_queue) {
        
        // 1.创建一个队列（非主队列）
        _queue = [[NSOperationQueue alloc] init];
        
        // 2.设置最大并发(最多同时并发执行3个任务)
        _queue.maxConcurrentOperationCount = 3;
    }
    return _queue;
}

如下图：

Simulator Screen Shot - iPhone 11 Pro Max - 2020-04-30 at 18.51.23.png

具体实现步骤，请看demo内容。

demo下载地址