PySide crashing when replacing rows in QFormLayout - qt

Question

Using the following code example PySide segfaults when pushing "Add", "Add", "Remove", "Add" and due to some other sequences of interaction.
Python: 2.7.6
PySide: 1.2.1
QtCore: 4.8.5
Code:
from PySide.QtGui import *
from PySide.QtCore import *
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setObjectName('MainWindow')
self.baseLayout = QWidget(self)
self.v_layout = QVBoxLayout(self.baseLayout)
self.setCentralWidget(self.baseLayout)
self.form_layout = QFormLayout(self.baseLayout)
self.v_layout.addLayout(self.form_layout)
self.button_add = QPushButton(self.baseLayout)
self.button_add.setText("Add")
self.v_layout.addWidget(self.button_add)
self.button_del = QPushButton(self.baseLayout)
self.button_del.setText("Remove")
self.v_layout.addWidget(self.button_del)
self.button_add.clicked.connect(self.add)
self.button_del.clicked.connect(self.remove)
self.fields = []
def add_item(self):
layout = QHBoxLayout(self.parent())
line = QLineEdit(self.parent())
slider = QSlider(self.parent())
layout.addWidget(line)
layout.addWidget(slider)
self.fields.append((layout, line, slider))
self.form_layout.addRow("Test", layout)
def add(self):
for i in range(15):
self.add_item()
def remove(self):
for (layout, line, slider) in self.fields:
line.deleteLater()
slider.deleteLater()
while self.form_layout.itemAt(0):
child = self.form_layout.takeAt(0)
if child.widget():
child.widget().deleteLater()
self.form_layout.update()
self.fields = []
def main():
import sys
app = QApplication(sys.argv)
frame = MainWindow()
frame.show()
app.exec_()
if __name__ == '__main__':
main()
Is this the correct way of adding compound widgets (in this case a QLineEdit and a QSlider within a QVBoxLayout) to a form layout? What am I doing wrong?

Answer 1

The correct way of adding "compound widgets" to a QFormLayout is to create a QWidget that will be the parent to that layout.
add_item() should rather look something like this:
def add_item(self):
widget = QWidget(self.parent())
layout = QHBoxLayout(widget)
line = QLineEdit(widget)
slider = QSlider(widget)
layout.addWidget(line)
layout.addWidget(slider)
self.fields.append((layout, widget, line, slider))
self.form_layout.addRow("Test", widget)
(And the widget also has to be removed when deleting the fields).

Answer 2

I think you are not creating the layouts in the right way, for example you are trying to set the layout of base_layout two times. Also you can check for count() on a QLayout to see if it has children:
from PySide.QtGui import *
from PySide.QtCore import *
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.baseLayout = QWidget(self)
self.v_layout = QVBoxLayout(self.baseLayout)
self.setCentralWidget(self.baseLayout)
self.form_layout = QFormLayout()
self.v_layout.addLayout(self.form_layout)
self.button_add = QPushButton()
self.button_add.setText("Add")
self.v_layout.addWidget(self.button_add)
self.button_del = QPushButton()
self.button_del.setText("Remove")
self.v_layout.addWidget(self.button_del)
self.button_add.clicked.connect(self.add)
self.button_del.clicked.connect(self.remove)
self.fields = []
def add_item(self):
layout = QHBoxLayout()
line = QLineEdit()
slider = QSlider()
layout.addWidget(line)
layout.addWidget(slider)
self.fields.append((layout, line, slider))
self.form_layout.addRow("Test", layout)
def add(self):
for i in range(15):
self.add_item()
def remove(self):
while self.form_layout.count() > 0:
child = self.form_layout.takeAt(0)
widget = child.widget()
if widget:
widget.deleteLater()
self.form_layout.update()
self.fields = []
def main():
import sys
app = QApplication(sys.argv)
frame = MainWindow()
frame.show()
app.exec_()
if __name__ == '__main__':
main()