connecting three comboboxes to control the options avaliable in qt - qt

Question

I have three comboboxes with three similar options, 'one', 'two', 'three', and I want to prevent the same option in different combobox.
Example:
combobox1 : 'one',
so when I go choose in combobox2 and combobox3 there's only 'two' and 'three' to choose from.
I know I could do this in a combination of for loop and if, but can anyone help me with some trick I could use here?

Answer 1

Write your own class MyComboBox which is derived from QComboBox.
Implement a slot in MyComboBox that would do something like this:
void excludeIndex(const QString & text)
{
// Get the list of all the options for the ComboBox
QStringList list = getIndices();
// Remove one (the only) item 'text' from the list
list.removeOne( text );
// Clear the ComboBox and fill with the new values
this->clear();
this->addItems( list );
}
In your parent widget/application, connect the signal void currentIndexChanged(const QString & text) from each 'sending' MyComboBox or QComboBox to this slot of the 'receiving' MyComboBox.
If you need to exclude the values from multiple other ComboBoxes, then it might be better to implement the slot in the parent Widget. That way, you can loop over all the 'receiving' ComboBoxes. Per ComboBox you will read all the current values of the other ComboBoxes and remove those values from list. Your slot in the parent Widget will not need an input QString anymore.

Answer 2

How about using only one combobox? There are only six possible options:
one two three
one three two
two one three
two three one
three one two
three two one
It would be much easier for the user to use only one combobox instead of using three comboboxes whose available options are continuously changing.

Answer 3

Here is one solution.
Basically it initializes all of the boxes with all the items, and as a box's current text is changed, it removes that text from the other boxes. If the previous text that the box contained wasn't blank, it adds it back into all the other boxes.
If you care to test it with more than 8, change the variable m_numOfBoxes in mainwindow.cpp to some other value.
main.cpp
#include <QApplication>
#include "mainwindow.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QComboBox>
#include <QList>
#include <QStringList>
#include <QMap>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void on_comboBox_changed();
private:
QList <QComboBox *> m_boxes;
QMap <QComboBox *, QString> m_previousText;
int m_numOfBoxes;
QStringList m_allItems;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include <QVBoxLayout>
#include <QDebug>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
QVBoxLayout * vbox = new QVBoxLayout();
m_numOfBoxes = 8;
m_allItems << "";
for(int i = 0; i< m_numOfBoxes; i++)
{
m_allItems << QString::number(i+1);
}
for(int i = 0; i< m_numOfBoxes; i++)
{
QComboBox * temp = new QComboBox;
QObject::connect(temp, SIGNAL(currentIndexChanged(int)), this, SLOT(on_comboBox_changed()));
vbox->addWidget(temp);
temp->addItems(m_allItems);
m_boxes.append(temp);
m_previousText[temp] = "";
}
this->setCentralWidget(new QWidget());
this->centralWidget()->setLayout(vbox);
}
MainWindow::~MainWindow()
{
}
void MainWindow::on_comboBox_changed()
{
QComboBox * editedBox = qobject_cast <QComboBox *> (QObject::sender());
QString currentText = editedBox->currentText();
if(currentText == m_previousText[editedBox])
{
return;
}
foreach(QComboBox * box, m_boxes)
{
if(box == editedBox)
{
continue;
}
if(currentText != "")
{
// remove the current text from the other boxes
int index = box->findText(currentText);
if(index != -1)
{
box->removeItem(index);
}
}
if(m_previousText[editedBox] != "")
{
// add the previous text back into the lists for the other boxes
box->addItem(m_previousText[editedBox]);
qDebug() << "Adding back" << m_previousText[editedBox];
}
}
m_previousText[editedBox] = currentText;
}
Note that when an item is added back into a box's list, it just gets tacked onto the end of the list, so over time the order of your items may get scrambled.
Hope that helps.