在单个 NSOperationQueue iOS 中管理多个操作，例如暂停/恢复单个操作 [英] Managing Multiple Operations in Single NSOperationQueue iOS like Pause/Resume single Operation

问题描述

在我的代码中，我想单独处理队列中的操作，并且能够暂停和恢复队列中的操作操作.我该如何实现?

In my code I want to handle operations individually in a queue and be able to pause and resume the operations operation in the queue. How can I implement that ?

让我简要解释一下我的问题，我使用以下代码通过子类 NSOperation 创建操作并将此操作添加到 NSOperationQueue.

Let me explain my question in brief, I have used below code for creating operation by subclass NSOperation and added this operation to NSOperationQueue.

@interface MyLengthyOperation: NSOperation
@end

@implementation MyLengthyOperation
- (void)main
{
    // a lengthy operation
    @autoreleasepool 
    {
        for (int i = 0 ; i < 10000 ; i++) 
        {

            // is this operation cancelled?
            if (self.isCancelled)
            break;

            NSLog(@"%f", sqrt(i));
        }
    }
}
@end

我已经创建了上面的操作，我用

I have created above operation and I am calling it with

NSOperationQueue *myQueue = [[NSOperationQueue alloc] init];
myQueue.name = @"Download Queue";
myQueue.maxConcurrentOperationCount = 4;
[myQueue addOperation:operation];

现在我想暂停并继续我的操作.让我们假设循环在 6786 上并且我按下了暂停按钮，那么队列应该暂停这个操作，当我按下开始时，它应该从 6786 开始.

Now I want to pause and resume my operation. Lets suppose that the loop is on 6786 and I pressed the pause button, then the queue should pause this operation and when I press start then it should start from 6786.

我想控制队列中的多个操作.我该怎么做?

I want to control multiple operations in the queue. How can I do that ?

我查看了 [queue setSuspended:YES]; - 这将阻止队列添加新操作，但我想控制队列中的现有操作.

I looked at [queue setSuspended:YES]; - this will prevent the queue from adding new operations but I want to control existing operations in queue.

等待您的答复.

提前致谢！

推荐答案

没有内置的暂停特定 NSOperation 的能力，如果你想要这种行为，那么你需要自己构建它.

The is no in-built ability to pause a particular NSOperation, if you want this behaviour then you need to build it yourself.

您可以使用 NSCondition 来执行此操作 -

You can use an NSCondition to do this -

@interface MyLengthyOperation: NSOperation

@property (atomic) BOOL paused;
@property (nonatomic,strong) NSCondition *pauseCondition;

@end

@implementation MyLengthyOperation

-(instancetype) init {
    if (self=[super init]) {
        self.pauseCondition=[NSCondition new];
    }
    return self;
}

- (void)main
{
    // a lengthy operation
    @autoreleasepool 
    {
        for (int i = 0 ; i < 10000 ; i++) 
        {

            // is this operation cancelled?
            if (self.isCancelled)
            break;

            [self.pauseCondition lock];
            while (self.paused) {
                [self.pauseCondition wait];
            }
            NSLog(@"%f", sqrt(i));
            [self.pauseCondition unlock];
        }
    }
}

-(void)pause {
    [self.pauseCondition lock];
    self.paused=YES;
    [self.pauseCondition signal];
    [self.pauseCondition unlock];
}

-(void)resume {
     [self.pauseCondition lock];
    self.paused=NO;
    [self.pauseCondition signal];
    [self.pauseCondition unlock];
}
777441end

然后你可以说[myOperation pause] 和[myOperation resume]

这篇关于在单个 NSOperationQueue iOS 中管理多个操作，例如暂停/恢复单个操作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！