How to change combobox store data in ExtJS 4.1

I define a combobox like this

{
  xtype: 'combobox',
  emptyText: 'Functions'
  store: [ 'none' ]
}

then, on some event the store should load new data, so I get the store from the combobox and try this:

oFunctionStore.loadData( ['dothis', 'dothat', 'dosomething' ] );

but after this, the combobox has a dropdown without any visible content, just tiny blank lines.