How to set additional properties on the tabs in a TabBar (Starling version)

TabBar supports setting a number of properties on its tabs through its dataProvider property, like label and isEnabled. Sometimes, we may need to set additional properties on the tabs. TabBar makes it easy to customize how its dataProvider is interpreted with the tabInitializer property.

The tabInitializer is a function that is called for each item in the data provider. The TabBar passes in a ToggleButton and an item from the data provider. The function signature looks like this:

function( tab:ToggleButton, item:Object ):void

If we want the TabBar to support additional properties on its tabs, we can pass in a custom tabInitializer. First, though, let's save a reference to the default tabInitializer in a variable because we want to preserve the default behavior:

var group:TabBar = new TabBar();
var defaultTabInitializer:Function = group.tabInitializer;

Now, we can create our own custom tabInitializer function that sets additional properties:

function customTabInitializer( tab:ToggleButton, item:Object ):void
	// keep the default behavior
	defaultTabInitializer( tab, item );

	// then add new properties!
	tab.scaleWhenDown = item.scaleWhenDown;

group.tabInitializer = customTabInitializer;

Notice that we call the defaultTabInitializer first. We still want to set properties like label and isEnabled.

Afterwards, we've also chosen to copy the scaleWhenDown property from the item to the tab.

If we wanted to make some properties optional, we could call hasOwnProperty() before setting them, like this:

if( item.hasOwnProperty( "scaleWhenDown" ) )
	tab.scaleWhenDown = item.scaleWhenDown;