Sort filenames naturally with Qt

Question

I am reading a directories content using QDir::entryList(). The filenames within are structured like this:

index_randomNumber.png

I need them sorted by index, the way the Windows Explorer would sort the files so that I get

0_0815.png
1_4711.png
2_2063.png
...

instead of what the sorting by QDir::Name gives me:

0_0815.png
10000_6661.png
10001_7401.png
...

Is there a built-in way in Qt to achieve this and if not, what's the right place to implement it?

Answer 1

If you want to use QCollator to sort entries from the list of entries returned by QDir::entryList, you can sort the result with std::sort():

dir.setFilter(QDir::Files | QDir::NoSymLinks);
dir.setSorting(QDir::NoSort);  // will sort manually with std::sort

auto entryList = dir.entryList();

QCollator collator;
collator.setNumericMode(true);

std::sort(
    entryList.begin(),
    entryList.end(),
    [&](const QString &file1, const QString &file2)
    {
        return collator.compare(file1, file2) < 0;
    });

---

According to The Badger's comment, QCollator can also be used directly as an argument to std::sort, replacing the lambda, so the call to std::sort becomes:

std::sort(entryList.begin(), entryList.end(), collator);

Answer 2

Qt didn't have natural sort implementation until Qt 5.2, see this feature request.

Since Qt 5.2 there is QCollator which allows natural sort when numeric mode is enabled.

Answer 3

Yes it is possible.

In order to do that you need to specify the flag LocaleAware when constructing the QDir. object. The constructor is

 QDir(const QString & path, const QString & nameFilter, SortFlags sort = SortFlags( Name | IgnoreCase ), Filters filters = AllEntries)

You can also use

QDir dir;
dir.setSorting(QDir::LocaleAware);