Hi, I ran into a bit of a brick wall when thinking about how to register to and dispatch to multiple micro-services and it made me realise the underlying tension came from not having peace about a fundamental design decision; how do you access your collaborators. Note: I am specifically talking about 'providers of functionality' as oppose to state. I think everybody agrees that passing state around is a "good thing" (e.g. *db* is so 90s, (defn my-thing-which-needs-a-db [db] ...) is where it is at).
One option is to receive instances of a service (probably some implementation of a defprotocol): (den my-service [service-1 service-2 payload] (some-method service-1) (some-method service-2)) The other is to directly reach into the collaborator's namespace: (den my-service [payload] (service-1-ns/some-function) (service-2-ns/some-function)) (maybe some config is passed into my-service which the other services use. The first approach has a much smaller coupling and makes it much easier to reason about. If there is coupling then it is on the protocol of the collaborator. It is therefore trivial to unit-test as you can stub out the collaborators without redef. It also has echoes of OO services, which might be just fine. The second approach means you don't end up passing collaborators deep down hierarchy graphs (which I haven't run into actually - Clojure tends to have a much 'flatter' graph then Java). It does mean testing etc. requires redefs. My inclination is to go for the first as it seems simpler, but I still have an allergic reaction to using protocols like this (because of the OO trap). This clearly isn't new ground, but I could find surprisingly little blogs and discussion about this. It is also something that only really becomes a problem in the larger scale as well. What do you all do? -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
