ReadLinesAsync()产生访问冲突 [英] ReadLinesAsync( ) produces access violation

问题描述

我编写了一个函数，该函数可以异步打开并读取文本文件，并将行写入向量中.我收到访问冲突.为什么?

I have written a function which asynchronously opens and reads a text file and write the lines into a vector. I am recieving an Access Violation. Why?

Windows::Foundation::Collections::IVector<Platform::String^>^ FileHandler::readFileReturnVectorWithLines(Platform::String^ filename)
{
	Windows::Foundation::Collections::IVector<Platform::String^>^ vector_of_lines;
	Windows::ApplicationModel::Package^ package = Windows::ApplicationModel::Package::Current;
	Windows::Storage::StorageFolder^ installedLocation = package->InstalledLocation;
	create_task(installedLocation->GetFileAsync(filename)).then([&vector_of_lines](Windows::Storage::StorageFile^ file)
	{
		return FileIO::ReadLinesAsync(file);
	}).then([&vector_of_lines](Windows::Foundation::Collections::IVector<Platform::String^>^ lines)
	{
		// The following line produces an access violation!
		vector_of_lines = lines;
	});
	return vector_of_lines;
}

推荐答案

您正在捕获"vector_of_lines"；通过引用，以及当"then"执行"vector_of_lines".参考不再有效.而是按值捕获，即"[vector_of_lines]".

You are capturing "vector_of_lines" by reference, and when the "then" is executed the "vector_of_lines" reference is no longer valid. Capture by value instead, i.e. "[vector_of_lines]".

此外，由于现在您的代码没有多大意义，因此您必须调用"wait"(等待).在返回"vector_of_lines"之前，在创建的任务上执行否则您应该返回任务< IVector< String ^>> ^>.现在，您正在返回的对象 不知道它是否有效(即异步任务是否仍在运行?).

Also, as it is now your code doesn't make much sense, either you have to call "wait" on the created task before returning "vector_of_lines" or you should return a task<IVector<String^>>^>. As it is now you are returning an object that you cannot know whether it is valid or not (i.e. is the asynchronous task still running or not?).

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