How do I get the selected index of an ExtJS Combobox

Question

What is the certified way to determine the index of the currently selected item in a ComboBox in ExtJS?

Is there a difference on how to do this between ExtJS 3.x and 4?

var combo = new Ext.form.ComboBox(config);
var selectedIndex = combo.selectedIndex; // TODO: Implement
if(selectedIndex > 2) {
    // Do something
}

Bonus-points for how to add it as a property to the ComboBox-object.

Answer 1

I think you'll have to use the combo's store for that. Combos have a private findRecord method that'll do a simple search over the store by property and value. You can see an example in the sourcecode itself (Combo.js line 1119).

1) Based on this you could find the selected index this way :

var v = combobox.getValue();
var record = combobox.findRecord(combobox.valueField || combobox.displayField, v);
var index = combobox.store.indexOf(record);

2) Or you could bind yourself to the "select" event which is fired with the combo, the record selected and its index as a parameter.

3) You could also access the view's getSelectedIndexes() but I doubt it's a good solution (in that I'm not sure it's available all the time)

Finally if you want to extend the combobox object I think this should work (if you go with the first solution) :

Ext.override(Ext.form.ComboBox({
  getSelectedIndex: function() {
    var v = this.getValue();
    var r = this.findRecord(this.valueField || this.displayField, v);
    return(this.store.indexOf(r));
  }
});