Zero instead of NULL in ComboBox (ExtJS 4.2)

Question

I'm working with an older version of ExtJS (4.2) and I have added a combobox to one of edit forms in my application.

The ComboBox looks like this:

Ext.define('RgiApp.view.ImjestoTipObjektaCombo2', {
extend: 'Ext.form.field.ComboBox',
alias: 'widget.imjestoTipObjektaCombo2',
requires: 'RgiApp.store.ImjestoTipObjektaStore2',
fieldLabel: 'Vrsta obilježja II',
name: 'vrstaobiljezjaid2',
displayField: 'name',
valueField: 'id',
matchFieldWidth: true,
queryMode: 'local',
forceSelection: false,
typeAhead: true,
minChars: 2,
//listWidth: 200,
//width: 200,
//minListWidth : 200,
store: 'RgiApp.store.ImjestoTipObjektaStore2'
});

The combobox is populated with records from database and it works fine, but when I edit a record that contains NULL value in this filed, the value sets to zero (picture below).

I want combobox to be empty if there is a NULL value, so It submits NULL if left so. This way, I have to manualy delete zero before submitting the form.

EDIT:

I added emptyText property to my combobox and now the form contains that text if I create new record, but it is still zero when I edit. These values are NULL in database.

Answer 1

Try to add emptyText property to your combobox definition. Ext.form.field.Text-cfg-emptyText Combobox iherits it from the Text field control.

Answer 2

I managed to solve this.

I set forceSelection to "true" and added beforeBlur function like this:

Ext.define('RgiApp.view.ImjestoTipObjektaCombo2', {
extend: 'Ext.form.field.ComboBox',
alias: 'widget.imjestoTipObjektaCombo2',
requires: 'RgiApp.store.ImjestoTipObjektaStore2',
fieldLabel: 'Vrsta obilježja II',
name: 'vrstaobiljezjaid2',
displayField: 'name',
valueField: 'id',
matchFieldWidth: true,
queryMode: 'local',
forceSelection: true,
typeAhead: true,
minChars: 2,
store: 'RgiApp.store.ImjestoTipObjektaStore2',
// Allow empty value in combobox
beforeBlur: function(){
    var value = this.getRawValue();
    if(value == ''){
        this.lastSelection = [];
    }
    this.doQueryTask.cancel();
    this.assertValue();
}
});

There are no more zeroes, now the combobox is blank if record in database is blank and it allow me to delete value so I can submit NULL.