[mattgreenrocks]

> you would keep a "pure" layer of domain code that does just that.

This is pretty much the only way I write 'business' software now. Even for small apps domain complexity gets gummed up with presentation/side effects really fast and I have a hard time disentangling them in my mind. Worth noting: most business apps I've worked on really don't have a lot of external dependencies, but those dependencies tend to sprawl out over the code quickly.

I'm really glad to see this approach getting traction in various forms (hexagonal programming, FP effect systems, Redux-style reducers) and don't have much of a horse in the race other than an abstract notion of a pure component, which may or may not be stateful, that accepts and sends a domain-specific set of messages and events.