How do you open a file using Symbian's RFile?

I have just started developing for Symbian. I am currently using Nokia Qt. I am trying to launch another application based on mime type. I currently am following this example. I'd like to attempt to open a .txt file.

I am finding it hard to understand how to create a RFile and what the TDesC16 class actually is / does?

In the example the code which basically does the work is following:

// Gets the UID and MIME type for the given file name.
TUid uid;
TDataType dataType;
User::LeaveIfError(session.AppForDocument(aFileName, uid, dataType));

// Runs the default application using the MIME type, dataType.
// You can also use the UID to run the application. 
TThreadId threadId;
User::LeaveIfError(session.StartDocument(aFileName, dataType, threadId));

The variable aFileName must be of type RFile. So how would开发者_开发百科 I create this object to open a .txt file stored at Computer\Nokia C7-00\Phone memory\test.txt (in Explorer).

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TDesC16 is a Symbian descriptor, which is basically a string. Here is a good manual: http://descriptors.blogspot.com/

As for your problem. In the example it looks like aFileName is meant to be a descriptor. So to open test.txt do something like this:

TThreadId threadId;
User::LeaveIfError(session.StartDocument(_L("c:\test.txt"), dataType, threadId));

If you want to go with RFile, here is a code sample:

RFs fs;
User::LeaveIfError(fs.Connect()); // connect to File Server
CleanupClosePushL(fs); // adding to the cleanup stack to ensure that the resources are released properly if a leave occurres while opening a file

RFile file;
User::LeaveIfError(file.Open(fs, _L("c:\test.txt"), EFileRead));
CleanupClosePushL(file);

// do something with file

CleanupStack::PopAndDestroy(2); // closes file and fs and removes them from the cleanup stack;