Hi,
I am trying to wrap my head around how to best use the Component library
for structuring my app.
Let's say I have a simple Store protocol:
(defprotocol Store
(get [store k])
(put [store k v]))
The production Store protocol implementation would, as an example, be
backed by Riak but in my tests I would like to mock it out with an
in-memory version. What would be the best way of doing so?
Option 1, separate lifecycle from the actual store:
(deftype InMemoryStore [backing-map]
Store
(get [_ k]
(@backing-map k))
(put [_ k v]
(swap! backing-map assoc k v)))
(defn create-memory-store
[]
(InMemoryStore. (atom {})))
;; create-fn must return something that implements the Store protocol
(defrecord StoreComponent [store create-fn]
component/Lifecycle
(start [component]
(assoc component :store (create-fn))
(stop [component]
(assoc component :store nil)))
(defn new-store [create-fn]
(map->StoreComponent {:create-fn create-fn}))
Option 2, create different components
(defrecord InMemoryStore [backing-map]
component/Lifecycle
(start [component]
(assoc component :backing-map (atom {}))
(stop [component]
(assoc component :backing-map nil))
Store
(get [_ k]
(@backing-map k))
(put [_ k v]
(swap! backing-map assoc k v)))
(defn new-memory-store []
(map->InMemoryStore {}))
And then inject the correct component in the system map depending on
settings.
Option 3, something completely different?
Both options seem quite cumbersome when all I want to be able to do in my
tests is to 'assoc' a map instead of a production Store implementation. Am
I just misunderstanding how to use the Component library?
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