Question

I’m trying to write code that appends ending _my_ending to the filename, and does not change file extension.

Examples of what I need to get:

"test.bmp"            -> "test_my_ending.bmp"
"test.foo.bar.bmp"    -> "test.foo.bar_my_ending.bmp"
"test"                -> "test_my_ending"

I have some experience in PCRE, and that’s trivial task using it. Because of the lack of experience in Qt, initially I wrote the following code:

QString new_string = old_string.replace(
      QRegExp("^(.+?)(\\.[^.]+)?$"),
      "\\1_my_ending\\2"
      );

This code does not work (no match at all), and then I found in the docs that

Non-greedy matching cannot be applied to individual quantifiers, but can be applied to all the quantifiers in the pattern

As you see, in my regexp I tried to reduce greediness of the first quantifier + by adding ? after it. This isn’t supported in QRegExp.

This is really disappointing for me, and so, I have to write the following ugly but working code:

//-- write regexp that matches only filenames with extension
QRegExp r = QRegExp("^(.+)(\\.[^.]+)$");
r.setMinimal(true);

QString new_string;

if (old_string.contains(r)){
   //-- filename contains extension, so, insert ending just before it
   new_string = old_string.replace(r, "\\1_my_ending\\2");
} else {
   //-- filename does not contain extension, so, just append ending
   new_string = old_string + time_add;
}

But is there some better solution? I like Qt, but some things that I see in it seem to be discouraging.

Answer 1

How about using QFileInfo? This is shorter than your ‘ugly’ code:

QFileInfo fi(old_string);
QString new_string = fi.completeBaseName() + "_my_ending" 
    + (fi.suffix().isEmpty() ? "" : ".") + fi.suffix();