QFileSystemModel::rowCount return 0

jronald

QFileSystemModel *model = new QFileSystemModel;
QString initPath("/");
model->setRootPath(initPath);
QModelIndex parentIndex = model->index(initPath);
bool ok = parentIndex.isValid();
if (ok)
{
    int numRows = model->rowCount(parentIndex);
    // numRows == 0, why?
    int numCols = model->columnCount(parentIndex);
    // numCols == 4, as expected
}

Christian Ehrlicher

You have to wait for QFileSystemModel::directoryLoaded()

jronald

@Christian-Ehrlicher said in QFileSystemModel::rowCount return 0:

You have to wait for QFileSystemModel::directoyLoaded()

OK, however in the doc Model/View Programming:

QFileSystemModel *model = new QFileSystemModel;
QModelIndex parentIndex = model->index(QDir::currentPath());
int numRows = model->rowCount(parentIndex);

PS: to locate the code, search numRows, the first one.

Christian Ehrlicher

I'll take a look at the docs later this day to see if it's correct.

JonB

@jronald , @Christian-Ehrlicher
You are right, that example (at link https://doc.qt.io/qt-5/model-view-programming.html#using-model-indexes) is not accurate for QFileSystemModel behaviour, it's intended to illustrate the principle of the code it's showing but has picked an unsuitable model.

From https://doc.qt.io/qt-5/qfilesystemmodel.html#caching-and-performance:

Unlike QDirModel, QFileSystemModel uses a separate thread to populate itself so it will not cause the main thread to hang as the file system is being queried. Calls to rowCount() will return 0 until the model populates a directory.

Perhaps therefore the docs example could just substitute QDirModel for QFileSystemModel in that light?

SGaist

@JonB No, the class is obsolete. The example should either use a different model or take into account the asynchronous nature of QFileSystemModel.

I'd go with the later.

SGaist

Documentation update is in progress.