How to manage file (replace, delete...) in Qt? - c++

Question

I've a text file with its backup copy: backup copy has the same name with only a "2" as last character of the extension (example: Original: Myfile.txt - Backup: Myfile.txt2).
Sometimes I need to replace the original one with the backup; I do the following:
QFile BackupFile("Myfile.txt2"); // backup copy
QString nameFile = BackupFile.fileName();// name of backup copy of file
nameFile.chop(1); // remove the last letter of file name, so nameFile now is the same of Original file
QFile originalFile(nameFile); // Original copy
originalFile.remove(); // delete the original file
BackupFile.rename(nameFile); // rename the backup file as original
BackupFile.close(); // close the file
This works, but it seems too complex. I'd like something easier.
Do you have any suggestion?

Answer 1

I think this code can be simple method. However, you should add code for error case, such as 'check whether backup file exist.', etc..
auto ReplaceWithBackup = []( QString& backupName ) -> bool
{
QString originName = backupName;
originName.chop( 1 );
if ( QFile::exists( originName ) )
{
QFile::remove( originName );
}
return QFile::rename( backupName, originName );
};
if ( ReplaceWithBackup( "Myfile.txt2") == false )
{
// error
}

Answer 2

If the files are in the same directory, you can use QDir::rename. Otherwise reading one file and writing in the other is required. Here is my version of the first case.
// Generate some test data
{
QFile bf( "Myfile.txt2" );
bf.open(QIODevice::WriteOnly);
bf.write("Backup data");
QFile( "Myfile.txt" ).open(QIODevice::WriteOnly);
}
//Assume you know which back-up file to restore
QString backupFn("Myfile.txt2");
//Actual code
QString origFn = backupFn.mid( 0, backupFn.size()-1 ); //"guess" the original file name.
QFile::remove( origFn ); //Use static version to delete file by name (No QFile instance required)
QDir().rename(backupFn,origFn);
However, each line requires many checks and validations e.g. is the provided backup-file name a valid backup name, did remove/rename succeded, etc, etc.