iOS中具有进度报告的可取消异步操作集 [英] Cancellable set of asynchronous operations with progress reporting in iOS

问题描述

假设我使用另一个SDK（我无法控制）和一个异步导入1个文件的API，并在完成时调用完成回调。
以下是一个示例API。

Suppose that I use another SDK (which I do not have control of) with an API that imports 1 file asynchronously, and calls a completion callback on completion. The following is an example API.

func importFile(filePath: String, completion: () -> Void)

我需要使用此API导入10个文件（逐个），但我需要它可以取消，例如在成功导入文件1,2,3之后，在导入文件4时，我希望能够取消整个操作集（导入10个文件），这样文件4就会完成（因为它已经开始了） ），但不再导入文件5-10。

I need to import 10 files (one by one) using this API, but I need it to be cancellable, e.g. after Files 1,2,3 has been successfully imported, while File 4 is being imported, I want to be able to cancel the whole set of operations (import of the 10 Files), such that File 4 will finish (since it already started), but Files 5-10 will not be imported anymore.

此外，我还需要报告导入的进度。成功导入文件1后，我应该报告10％的进度（10个中有1个已完成）。

In addition, I also need to report progress of the import. When File 1 has been imported successfully, then I should report progress of 10% (1 out of 10 has been finished).

我如何实现这一目标？

我正在考虑使用NSOperationQueue和10个NSOperations，但似乎进度报告很难。

I am considering using NSOperationQueue with 10 NSOperations, but it seems that progress reporting will be difficult.

推荐答案

所以，我相信你想从你的问题中得到以下内容：

So, I believe that this is the following you want from your question:

1. 逐个导入n个文件队列


2. 导入每个文件时的报告进度


3. 能够在中间取消操作

可以通过以下方式使用 NSOperationQueue 和 NSBlockOperation 来实现。

It can be achieved using NSOperationQueue and NSBlockOperation in the following way.

1. 创建 AsyncBlockOperation 和 NSOperationQueue + AsyncBlockOperation 来自以下StackOverflow问题的答案中给出的代码类： NSOperation等待异步块执行


2. 将这两个类导入到将要使用的文件中



3. 创建操作队列

1. Create AsyncBlockOperation and NSOperationQueue+AsyncBlockOperation classes from code given in answer for the following StackOverflow question: NSOperation wait until asynchronous block executes
2. Import both the classes into the file they are going to be used

3. Create an operation queue

NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
operationQueue.maxConcurrentOperationCount = 1;
operationQueue.name = @"com.yourOrganization.yourProject.yourQueue";

创建一个函数，为您提供回调以获取进展

Create a function which gives you a callback for getting progress

- (void)importFilesFromFilePathArray:(NSArray *)pathsArray
                    inOperationQueue:(NSOperationQueue *)operationQueue
                        withProgress:(void (^)(CGFloat progress))progressBlock {

  }

在 2 中定义的函数，使用 NSBlockOperation 在 NSOperationQueue

Inside the function defined in 2, use NSBlockOperation for performing your operations in the NSOperationQueue

for (int i = 0; i < pathsArray.count; i++) {

    [operationQueue addAsyncOperationWithBlock:^(dispatch_block_t completionHandler) {
        [self importFile:(NSString *)[pathsArray objectAtIndex:i] completion:^(bool completion) {
            [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                CGFloat progress = (100 * (float)(i+1)/pathsArray.count);
                progressBlock(progress);
                if (progress == 100) {
                   successBlock(YES);
                }
             }];
             completionHandler();
         }];
     }];
}

对于取消操作，我们只需使用我们在第一步创建的operationQueue

[operationQueue cancelAllOperations];

我自己试过这段代码。它运作良好。随意提出改进建议，使其更好：）

I tried this code myself. It's working well. Feel free to suggest improvements to make it better :)

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