How can I interlink two QComboBoxes with C++ using Qt

Question

I'm trying to improve my UI to interlink two combo boxes with each other.

My xml file contains:

<DBInfo>
  <Info Org_Id="4" Database="ORACLE~orcl206~sample~2B3F1084DC06~~" />
  <Info Org_Id="5" Database="ORACLE~sample1~sample1~20E786F40DF7~~" />
</DBInfo>

I'm reading data from the xml file and placing all org_Id (4, 5) in one QStringList orgidlst and placing all database usernames (sample, sample1) in another QStringList dbnamelst . I'm adding items to two QComboBoxes with these string lists:

orgidcombobox.additems(orgidlst);
DBNamecombobox.additems(dbnamelst);

Up to now working fine, but now if I want to change the item name in DBNamecombobox to sample1 , then orgidcombobox shall be 5 , if I change orgidcombobox to 4 , then DBNamecombobox shall change to sample viceversa.

Answer 1

Comment from ni1ight is a good solution (I'm copying it at the end for completeness). On the other hand, if your combo boxes are sorted, then you must use something more complex. I find useful using the item data for storing DB keys and then use that to find any element, even if indices don't match anymore:

for (int ii = 0; ii < orgidlst.count(); ++ii) {
  comboBox1->addItem(orgidlst[ii], orgidlst[ii]);
  comboBox2->addItem(dbnamelst[ii], orgidlst[ii]);
}

connect(comboBox1, SIGNAL(currentIndexChanged(int)), SLOT(onComboIndexChanged(int)));
connect(comboBox2, SIGNAL(currentIndexChanged(int)), SLOT(onComboIndexChanged(int)));

The common slot may look like the code below, the magic resides in the QComboBox::findData method:

void YourClass::onComboIndexChanged(int) {
  // Find the current and the other combo
  auto the_combo = qobject_cast<QComboBox*>(sender());
  if (combo1 == nullptr) return;
  auto the_other_combo = the_combo == comboBox1 ? comboBox2 : comboBox1;

  const int the_other_index = the_combo->findData(the_combo->currentData());
  the_other_combo->setCurrentIndex(the_other_index);
}

ni1ight solution

Works if both combo boxes preserve the elements ordering:

connect(comboBox1, SIGNAL(currentIndexChanged(int)), comboBox2, SLOT(setCurrentIndex(int)));
connect(comboBox2, SIGNAL(currentIndexChanged(int)), comboBox1, SLOT(setCurrentIndex(int)));