UMG Viewmodel for Unreal Engine (for infant babies)

INFO

This is not an official documentation site, alright? You can find the Official Documentation for UMG Viewmodels here

What Is Model View Viewmodel?

Model-View-Viewmodel (MVVM) is a pretty common pattern in a lot of software development. More specifically, it's useful because it's a clean separation of concerns between the way user interface data is shown and the way it's exposed from something like a gameplay system to the UI.

Separating Logic From Presentation

"Separating logic from presentation" is a phrase you hear a lot, because it tackles something very muddy: UI doesn't often know the best way to get information from the game. Without a clear way to do it, you end up with many people taking many approaches to get UI. In Unreal Engine, this happens a lot. In separating logic from presentation, you make UI very, very "stupid" and you can make reasonable assumptions about what UI should show.

Viewmodels Enable Stupid UI

In my opinion, User interface elements should be stupid. They should be very dumb. In engineering we'd say that UI should be "stateless" in that it should be a clear and calculable representation of its input. It shouldn't contain surprises or track things that it's not responsible for. If I have a button widget, I don't want that button widget to know anything except for what its content should be and what function it should call when it's clicked.

A Viewmodel in this case, is something a widget would "bind" to. The widget would bind to values on the Viewmodel and update when the viewmodel changes. The UI no longer has to track things, it has now delegated that responsibility to the Viewmodel. If we were making an Ocean's Eleven analogy, the UI is "The Looks" and the Viewmodel is "The Brains"