iOS - 如何知道 NSOperationQueue 何时完成处理一些操作? [英] iOS - How to know when NSOperationQueue finish processing a few operations?

问题描述

我需要在我的应用程序中下载目录及其内容.所以我决定实现一个 NSOperationQueue 并且我子类化 NSOperation 来实现 NSURLRequest 等......

I need in my application to download directories and their content. So I decided to implement a NSOperationQueue and I subclassed NSOperation to implement NSURLRequest etc...

问题是我一次添加了所有操作，但我无法确定何时下载一个目录的所有文件以更新 UI 并启用此特定目录.

The problem is I add all the operations at once and I can't figure out when all the files for one directory are downloaded in order to update the UI and enable this specific directory.

现在我必须等待所有目录中的所有文件都下载完毕才能更新 UI.

Now I have to wait that all the files from all the directories are downloaded in order to update the UI.

我已经为 NSOperationQueue 的 operationCount 和 NSOperation 的 isFinished 实现了键值观察，但我不知道一个目录什么时候包含所有文件！

I already implemented key-value observing for the operationCount of the NSOperationQueue and the isFinished of the NSOperation but I don't know when a directory has all the files in it !

你有什么想法吗?

非常感谢

推荐答案

添加一个完成"NSOperation，它具有一个目录的所有其他 NSOperations 作为依赖项.

Add a "Done" NSOperation which has all other NSOperations for one directory as dependency.

像这样:

NSInvocationOperation *doneOp = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(done:) object:nil];

NSInvocationOperation *op1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(doSomething:) object:nil];
[queue addOperation:op1];
[doneOp addDependency:op1];

NSInvocationOperation *op2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(doSomething:) object:nil];
[queue addOperation:op2];
[doneOp addDependency:op2];

NSInvocationOperation *op3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(doSomething:) object:nil];
[queue addOperation:op3];
[doneOp addDependency:op3];

[queue addOperation:doneOp];

doneOp 只会在 op1、op2 和 op3 执行完毕后运行.

doneOp will only run after op1, op2 and op3 have finished executing.

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