ObjectA.Signal.connect(ObjectB.Slot) not working. is my understanding correct?

Question

This is my understanding of Signal and Slot, is it correct?

When clicked, emitting a data(QModelIndex) to setRootIndex().

if correct. then why this code not working?

treeView.clicked.connect(listView.setRootIndex)

this is my ui:

code:

... ...
# model
treeModel=QtWidgets.QFileSystemModel()
listModel=QtWidgets.QFileSystemModel()
treeModel.setRootPath(PATH1)
listModel.setRootPath(PATH2)

# fill data
treeView.setModel(treeModel)
treeView.setRootIndex(treeModel.index(PATH1))
listView.setModel(listModel)
listView.setRootIndex(listModel.index(PATH2))

# connect
treeView.clicked.connect(listView.setRootIndex)

# show window
... ..

Answer 1

When you execute your code you get the following message:

QAbstractItemView::setRootIndex failed : index must be from the currently set model

And that message gives us an important clue, a QModelIndex belongs to a model so although it has the same data from another QModelIndex of another model they are not the same.

There are 2 possible solutions:

• Use only one model

import os
from PyQt5 import QtCore, QtGui, QtWidgets

if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)

    model = QtWidgets.QFileSystemModel()
    model.setRootPath(QtCore.QDir.rootPath())

    treeView = QtWidgets.QTreeView()
    treeView.setModel(model)
    treeView.setRootIndex(model.index(QtCore.QDir.homePath()))

    listView = QtWidgets.QListView()
    listView.setModel(model)
    listView.setRootIndex(model.index(QtCore.QDir.homePath()))

    treeView.clicked.connect(listView.setRootIndex)

    w = QtWidgets.QWidget()
    hlay = QtWidgets.QHBoxLayout(w)
    hlay.addWidget(treeView)
    hlay.addWidget(listView)
    w.show()

    sys.exit(app.exec_())

• Obtain the QModelIndex of the other model using the QModelIndex information of the initial model:

import os
from PyQt5 import QtCore, QtGui, QtWidgets

if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)

    dirModel = QtWidgets.QFileSystemModel()
    dirModel.setRootPath(QtCore.QDir.rootPath())
    dirModel.setFilter(QtCore.QDir.NoDotAndDotDot | QtCore.QDir.Dirs)

    listModel = QtWidgets.QFileSystemModel()
    listModel.setRootPath(QtCore.QDir.rootPath())

    treeView = QtWidgets.QTreeView()
    treeView.setModel(dirModel)
    treeView.setRootIndex(dirModel.index(QtCore.QDir.homePath()))

    listView = QtWidgets.QListView()
    listView.setModel(listModel)
    listView.setRootIndex(listModel.index(QtCore.QDir.homePath()))

    treeView.clicked.connect(
        lambda ix: listView.setRootIndex(
            listModel.index(ix.data(QtWidgets.QFileSystemModel.FilePathRole))
        )
    )

    w = QtWidgets.QWidget()
    hlay = QtWidgets.QHBoxLayout(w)
    hlay.addWidget(treeView)
    hlay.addWidget(listView)
    w.show()

    sys.exit(app.exec_())