Looks like the delegate / data source pattern [1] which is prevalent in Cocoa programming.<p>[1] <a href="https://developer.apple.com/library/archive/documentation/General/Conceptual/CocoaEncyclopedia/DelegatesandDataSources/DelegatesandDataSources.html" rel="nofollow">https://developer.apple.com/library/archive/documentation/Ge...</a>