Chapter 1

Update view
iAppView->DrawNow();
}
The normal sequence of processing here is that I invoke the dialog (using the terse syntax
that was covered in Chapter 10), write the file, and redraw the app view to reflect the new
iText value.
If WriteFileL() leaves, I handle it by deleting iText and setting its pointer to 0. I also
delete the file. Then I redraw the app view and use User::Leave() to propagate the error
so that Uikon can display an error message corresponding to the error code. Test this, if you
like, by inserting User::Leave(KErrDiskFull) somewhere in WriteFileL().
The trap handler has one virtue: it lets the user know what's going on. It's still not good
enough for serious application use, though, because this approach loses user and file data.
It's a cardinal rule that Symbian OS shouldn't do that. A better approach would be to do the
following:
� Write the new data to a temporary file: if this fails, keep the user data in RAM, but
delete the temporary file.
� Delete the existing file: this is very unlikely to fail, but if it does, keep the user data in
RAM but delete the temporary file.
� Rename the temporary file: this is very unlikely to fail, and if it does, we're in trouble.
Keep the user data in RAM anyway.
I would need to restructure my program to achieve this; the application architecture's
framework for load/save and embeddable documents looks after these issues for you.
For database-type documents, you face these issues with each entry in the database. They
are managed by the permanent file store class, which we'll encounter below.
13.4.3 Reading it Back
The code to read the data we have written is similar. Firstly, we read the filename from a
dialog and then use OkToExitL() to do some checking. This time, the code is much easier
and I'll present it in one segment:
TBool CExampleReadFileDialog::OkToExitL(TInt /* aKeycode */)
// Termination
{
// Get filename
CEikFileNameEditor* fnamed=static_cast
(Control(EExampleControlIdFileName));
HBufC* fileName = fnamed->GetTextInHBufL();
// Check it's even been specified
if(!fileName)
{
TryChangeFocusToL(EExampleControlIdFileName);
iEikonEnv-
>LeaveWithInfoMsg(R_EIK_TBUF_NO_FILENAME_SPECIFIED);
}