Chapter 1

The code makes a simple MkDirAll() call. This time you can see why RFs functions don't
leave with an error code: I'm happy if either the directories didn't exist and they were created
successfully, or they did exist and nothing happened. Otherwise, I initiate a leave.
Now things get more delicate. I tentatively create the file, by opening it:
// Check whether it's going to be possible to create the
file for writing
RFile file;
err = file.Create(iCoeEnv->FsSession(), *fileName, EFileWrite);
if(err != KErrNone && err != KErrAlreadyExists)
User::Leave(err); // No need to close file, since it didn't open
RFile::Create() creates a new file if possible. If the file was already there, err contains
KErrAlreadyExists: I want to know whether the user really wants to replace this file, and
I'll check that in the next step. If the file wasn't there, but was created successfully by
RFile::Create(), then err is set to KErrNone. In any other case, I leave.
If I had wanted to replace the file without checking with the user, I would have used
RFile::Replace() to open the file. As it is, I want to check with the user:
// Check whether the user wants to replace the file,
if it already exists
if(err == KErrAlreadyExists)
{
if(iEikonEnv->QueryWinL(R_EIK_TBUF_FILE_REPLACE_CONFIRM))
else
}
User::LeaveIfError(file.Replace(iCoeEnv->FsSession(),
*fileName,
EFileWrite));
iEikonEnv->LeaveWithInfoMsg(0); // Let user try again
If the attempt to create the file revealed that it already existed, I use a UIQ query dialog to
confirm with the user. If the user insists, then I open the file again with RFile::Replace().
Any errors this time must be genuine errors, so I don't have to check specific codes – I
simply enclose the call with User::LeaveIfError().
But if the user didn't want to replace the file, I leave silently with iEikonEnv-
>LeaveWithInfoMsg(0). The leave helps to ensure that anything I've pushed to the
cleanup stack is popped and destroyed. The 0 indicates that I'm not passing a resource ID of
a message, because I don't want a message – none is needed, since the user knows exactly
what has happened: they just replied No to a query.
Now I've done all the checks I need to make. I've verified user input and I've verified that I
can create the file for writing.
I prefer to separate UI code (like this) from engine code (which actually does things, like
writing files), so I don't write the file from this function. Instead, I pass the parameters back to
the app UI, which will process them when I return: