How to add extra data to qfilesystemmodel items?

Question

I'm trying to make an pyqt app, which examines directory structure and the files in it. What I want to do is to add some extra info to the items in the qfilesystemmodel, for example, tagging files as 'checked' or 'unchecked'. I have found that each item (file or folder) in the model has four columns, name, size, timestamp and type. Is it possible to make the item have fifth column, which will contain custom information (tags) ? Or, Is there any way to annotate extra info on the items in the model ? If not, I think I have to have another model, such as qstanarditemmodel, to keep the tags. But I don't want it to be in a saperated model. Thanks!

Answer 1

In short, no, not easily. The Qt developers stopped working on QFileSystemModel for complexity reasons. Basically, the backend file system engine is way too complex and fragile, and QFileSystemModel relies entirely upon it.

You could reimplement QFileSystemModel, but it would require a lot of painful work and accessing the private headers.

Answer 2

The QFileSystemModel class delegates to a live file-system. So it doesn't really contain any items that you can add information to. The items are actually the files and directories inside the file-system.

Given this, it follows that a second data structure will be required to hold the additional information. Otherwise, you'd need to somehow store the information in the files and directories themselves. This might be possible for certain file-types (e.g. images). But it is obviously unfeasible to do this for arbitrary file-types.

It should be possible to sub-class QFileSystemModel and reimplement the usual methods so that extra columns can be added. As a bare minimum, you would need to reimplement columnCount() and data() - but obviously the exact details of how you go about this will depend on the data structure you choose to hold the additional information. Very roughly, it might look something like this:

class FileSystemModel(QFileSystemModel):
    def __init__(self, parent=None):
        super(FileSystemModel, self).__init__(parent)
        self._data = DataStructure()

    def columnCount(self, parent):
        return super(FileSystemModel, self).columnCount(parent) + 1

    def data(self, index, role):
        if index.isValid() and index.column() == self.columnCount() - 1:
            if role == QtCore.Qt.DisplayRole:
                # return the relevant additional data
            elif role == QtCore.Qt.CheckStateRole:
                # etc, etc
        else:        
            return super(FileSystemModel, self).data(index,role)