QRadioButton group and QDataWidgetMapper

jmelbye

I wanted to be able to represent an exclusive set of options as several radio buttons. I also wanted to be able to store an integer Id corresponding to which option was selected in my database, and ideally, use QDataWidgetMapper to do it. Yes, a combo box could serve here, but for this particular UI, I would prefer option buttons (in part because there are other widgets that become enabled/disabled as a result of the selected option, and they are laid out in a way that helps make the relationship apparent.)

I came across QButtonGroup and thought that might solve my problem, but QButtonGroup is not a QWidget, which is needed by QDataWidgetMapper. I also came acroos QGroupBox which is a QWidget, but it doesn't have a property to get at the currently selected option (and why should it - a group box could have all sorts of different sets of child items.)

I thought this would be a fairly common problem, so I wanted to present my solution so that:

Those of you who have tackled this problem before can chime in on the solution
Those of you who are looking for a solution have a starting place

I wanted to use a widget as a starting place, and then add to the interface:

A method for assigning an integer Id to each option button
A property for getting/setting the current Id / selected option button

The currently selected propery needs to be a property in order to work with QDataWidgetMapper. The best widget to use as a starting place seemed to be...well...QWidget!

Here is my OptionGroup class:

optiongroup.h
@
#ifndef OPTIONGROUP_H
#define OPTIONGROUP_H

#include <QWidget>
#include <QMap>

class QRadioButton;

class OptionGroup : public QWidget
{
Q_OBJECT
Q_PROPERTY(int currentSelection READ currentSelection WRITE setCurrentSelection USER true)

public:
explicit OptionGroup(QWidget *parent = 0);

int currentSelection() const;
void setCurrentSelection(int selection);

void setSelectionId(QRadioButton *button, int id);

signals:
void selectionChanged(int selection);

public slots:
void buttonToggled(bool checked);

private:
int currentSelection_;
QMap<int, QRadioButton*> buttonMap_;
QMap<QRadioButton*, int> revButtonMap_;
};

#endif // OPTIONGROUP_H
@

optiongroup.cpp:
@#include <QRadioButton>
#include "optiongroup.h"

OptionGroup::OptionGroup(QWidget *parent) :
QWidget(parent), currentSelection_(-1)
{
}

int OptionGroup::currentSelection() const
{ return currentSelection_; }

void OptionGroup::setCurrentSelection(int selection)
{
// If the specified selection id is not in our button map,
// then it is invalid, set selection to -1. Otherwise,
// update the selection to user specified value

auto iter = buttonMap_.find(selection);
if (iter == buttonMap_.end() || selection < 0) {
    currentSelection_ = -1;
    for (iter = buttonMap_.begin(); iter != buttonMap_.end(); ++iter)
        iter.value()->setChecked(false);
} else {
    iter.value()->setChecked(true);
    currentSelection_ = selection;
}

}

void OptionGroup::setSelectionId(QRadioButton* button, int id)
{
// Make sure we got a valid Id (non-negative)
// Also then listen for signals from this button
if (id >= 0) {
buttonMap_[id] = button;
revButtonMap_[button] = id;
connect(button, SIGNAL(toggled(bool)), this, SLOT(buttonToggled(bool)));
}
}

void OptionGroup::buttonToggled(bool checked)
{
if (checked == true) {
QRadioButton* btn = qobject_cast<QRadioButton*>(sender());
Q_ASSERT(btn);
currentSelection_ = revButtonMap_[btn];
emit selectionChanged(currentSelection_);
}
}
@

Note that you'll need to call setSelectionId() to assign an Id to each QRadioButton. -1 is used to represent an invalid or unset Id, so be sure to pass something that is greater than or equal to 0.

If you had:

ui->optBtnA which corresponds with Id 0
ui->optBtnB which corresponds with Id 1
ui->optBtnC which corresponds with Id 2

And they were all children of an OptionGroup ui->optionGroup, you would do this:
@
ui->optionGroup.setSelectionId(ui->optBtnA, 0);
ui->optionGroup.setSelectionId(ui->optBtnB, 1);
ui->optionGroup.setSelectionId(ui->optBtnC, 2);

...
// QDataWidgetMapper mapper;
// int optionField; This is which field in your data model you are storing the option value in
mapper.addMapping(ui->optionGroup, optionField);
@

This seems to be working well enough. Having the two maps for looking up Ids/QRadioButton* is redundant. Since the list of options is always likely to be pretty small, so I might use a QList of QPair's and just sequentially search them.

Hit me with your critiques, and hope this helps somebody else out.

rivimey

Looks really useful for the right situation... thanks for taking the trouble to post it :-)

lvlvlvl

Code translated in Pyside :

@
from PySide.QtCore import *
from PySide.QtGui import *

class optionGroup(QWidget):

def init(self, parent):
QWidget.init (self, parent)
self.ListeBoutons = []
self.currentSelection_ = -1

def litSelection (self):
return self.currentSelection_

def setCurrentSelection (self, selection):
self.currentSelection_ = -1
for elem in self.ListeBoutons:
if elem[1] == selection:
elem[0].setChecked(True)
self.currentSelection_ = selection

def setSelectionId (self, Bouton, ident):
self.ListeBoutons.append([Bouton, ident])
Bouton.toggled[bool].connect(self.buttonToggled)

def buttonToggled (self, checked):
if checked:
Bouton = self.sender()
for elem in self.ListeBoutons:
if elem[0] == Bouton:
self.currentSelection_ = elem[1]
self.selectionChanged.emit(self.currentSelection_)

currentSelection = Property(int, litSelection, setCurrentSelection, user = True)
selectionChanged = Signal(int)
@

mananbhatt

Hi jmelbye

can u please elaborate how to provide Id for each and every radiobutton and then store in mdoel

mananbhatt

Hi jmelbye

can u please elaborate how to provide Id for each and every radiobutton and then store in mdoel

mananbhatt

and also i get this error while exec
error: 'QMap<Key, T>::iterator::operator bool() const [with Key = int, T = QRadioButton*]' is private

mananbhatt

and also i get this error while exec
error: 'QMap<Key, T>::iterator::operator bool() const [with Key = int, T = QRadioButton*]' is private