I'm a fan of the Hexagonal Architecture / Ports-and-Adapters pattern. I'm used to implementing it with =defprotocol= and =defrecord= in Clojure, but this approach has drawbacks when you add Clojure Spec to the mix. I explored (very lightly!) three approaches:
The TL;DR is that the last one plays much better with Spec than the other two approaches.
Specifically, if I made changes to the =uses= namespace and re-evaluated that into my REPL, I struggled to get my demo to work without launching a fresh repl. (Sometimes I could make it work with a carefully ordered re-eval of the other files, but not always.) The map-of-functions approach was much more forgiving.
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