iOS - 如何知道NSOperationQueue何时完成处理几个操作？ [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和我的子类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...

问题是我一次添加所有的操作，我无法弄清楚当下载一个目录的所有文件，以便更新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被下载以更新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，但是我不知道什么时候有目录中的所有文件！

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 其中包含所有其他 NSOperations 为一个目录作为依赖。

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

如下所示：

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 已执行完毕。

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

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