Oh, it looks like I also forgot to include
itemToHeaderText in the example. For the example collection, the function is actually exactly the same as
groupListView.itemToHeaderText = (item:Dynamic) -> item.text;
EDIT: Actually, I've now changed the example collection to use
headerText as the property name for the group's text, instead of
text. This should make it more clear why there are separate functions for groups and items inside groups. You can continue using
text, or you can change your code to match the new naming scheme. It's up to you. The reason why
itemToHeaderText exist is to ensure that it works with any property name to better support real-world data structures.