How to Prevent Qt Designer from Overwriting Custom Code During UI Modifications?

Qt Designer Override Issue: Preserving Code Modifications During UI Changes

When using Qt Designer to design a GUI, it is common practice to make changes to the generated code for specific functionalities. However, these modifications can be lost upon subsequent UI changes.

Solution:

To avoid this issue, it is recommended to separate the UI design from the custom code. This can be achieved by creating a new class that inherits from the Qt Designer class and includes the logic you want to preserve.

For instance, if the Qt Designer design is named Ui_Design.py, the following code structure can be used:

# Ui_Design.py
from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        [...]

    def retranslateUi(self, MainWindow):
        [...]

Create a separate file, logic.py, to implement the custom logic and use the design as follows:

# logic.py
from PyQt5 import QtCore, QtGui, QtWidgets
from Ui_Design import Ui_MainWindow

class Logic(QMainWindow, Ui_MainWindow):
    def __init__(self, *args, **kwargs):
        QMainWindow.__init__(self, *args, **kwargs)
        self.setupUi(self)

By adopting this approach, even if the UI design is modified and re-generated, the custom code in logic.py will remain intact.

Additional Note: Class Structure for Custom Logic

To implement this effectively, the custom logic class must follow a specific structure:

class Logic(PyQtClass, DesignClass):
    def __init__(self, *args, **kwargs):
        PyQtClass.__init__(self, *args, **kwargs)
        self.setupUi(self)

where:

• PyQtClass depends on the Qt Designer template used (e.g., QMainWindow for MainWindow template)
• DesignClass is the name of the class in the design file (e.g., Ui_MainWindow)

Example of Preserving Code for Closing Message Box:

class Logic(QMainWindow, Ui_MainWindow):
    def __init__(self, *args, **kwargs):
        QMainWindow.__init__(self, *args, **kwargs)
        self.setupUi(self)
    def closeEvent(self, event):
        answer = QtWidgets.QMessageBox.question(
            self,
            'Are you sure you want to quit ?',
            'Task is in progress !',
            QtWidgets.QMessageBox.Yes,
            QtWidgets.QMessageBox.No)
        if answer == QtWidgets.QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()

This implementation ensures that your custom logic, such as the closeEvent handler, remains unaffected by subsequent UI changes made with Qt Designer.

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