I love this pattern. I agree with the author that design patterns that only exist because, say, your programming languages doesn't have function types, aren’t w

I love this pattern. I agree with the author that design patterns that only exist because, say, your programming languages doesn't have function types, aren’t worth writing a book on. This pattern seems like a specific application of the general idea to favor data structures over logic. If you manage to make a clear datastructure that encapsulates all the different ways in which your data/users/etc might behave, the implementation of the logic is often very straight forward. Conversely, if your data structure is either too generic or too specific, you end up having to code a lot of special cases, exceptions, mutable state and so on in the logic to deal with that.