Initialisation Order about integrant HOT 5 CLOSED

Why do you require :license to evaluate before :server? What does it do?

Also, do you know about prep-key and resolve-key?

from integrant.

My example is slightly contrived, but lets say I want the license state to evaluate first as it may cause the system initialisation to stop and I want to ensure the server (or other, possibly side-effecting sub-system) has not started prior.

prep-key and resolve-key relate to a single key, I'm interested in controlling the initialisation order of otherwise unrelated sub-parts of a system.

from integrant.

It sounds like you still have a dependency between :license and :server, but you're not interested in the data, just whether or not the initialization was valid.

You can set up automatic relations with prep-key. For example:

(defmethod ig/prep-key :app/server [_ opts]
  (assoc opts ::depends-on (ig/ref :app/license)))

You can use ig/refset to make it an optional dependency:

(defmethod ig/prep-key :app/server [_ opts]
  (assoc opts ::depends-on (ig/refset :app/license)))

from integrant.

Thanks James, I'm struggling to remember the usual cases but I expect generally there's an external, stateful co-dependency where I'm not interested in the data but do require a creation order within my system.

I'll give prep-key and/or refset a go, seems like that will work.

from integrant.

Interesting discussion. I usually tend to prefer the config approach as in @d-t-w 's initial message, so if you have to change the init order you don't have to change the code, but only the config. But in the case of a license, the prep-key seems like a good solution.

from integrant.