pharmacist.data-source — cjohansen/pharmacist 0.2019.02.03-4

Tools for implementing data sources

cache-deps clj/s multimethod

Specify which dependencies are relevant to compute a cache key. Should return a set of dependencies. The default implementation extracts the dependencies from the result from [cache-params]. Most use-cases are best solved using [cache-params], and in the rare cases where you need to control cache dependencies manually, it is recommended to specify it declaratively in your sources:

(require '[pharmacist.data-source :as data-source])

(def my-source
  {::data-source/fn #'fetch-my-source
   ::data-source/params {:id ^::data-source/dep [:dep1 :id]
                         :type ^::data-source/dep [:dep2 :type]}
   ::data-source/cache-deps #{:dep1}})

cache-key clj/s multimethod

Given a source, return the cache key that uniquely addresses content loaded by the source. The default implementation combines the id/type with the [cache-params]. It is strongly recommended to make sure the source's variations are expressed as parameters so you can rely on the default implementation of this method. If this is somehow not possible, you can implement this method, which dispatches on a source's :pharmacist.data-source/id, to provide a custom cache key:

(require '[pharmacist.data-source :as data-source])

;; This is just an example, NOT recommended. Environment variables could just as
;; easily be fed in as parameters
(defmethod data-source/cache-key ::my-source [source]
  [(get (System/getenv) "app_env") (-> source ::data-source/params :id)])

cache-params clj/s multimethod

Selects which parameters to use to calculate the cache key for a source. Should return a vector of paths to extract from the source after all dependencies are resolved. Specify cache-params declaratively in your sources instead of implementing this method.

(require '[pharmacist.data-source :as data-source])

(def my-source
  {::data-source/fn #'fetch-my-source
   ::data-source/params {:id ^::data-source/dep [:dep1 :id]
                         :type ^::data-source/dep [:dep2 :type]}
   ::data-source/cache-params [[:dep1 :id]]})

fetch clj/s multimethod

Fetch a source asynchronously. This method is dispatched on the :pharmacist/data-source/id key of the source. If no :pharmacist.data-source/fn or :pharmacist.data-source/async-fn is provided, this method is called with a single source. It should return a clojure.core.async/chan that emits a single message, which should be one of [parmacist.result/success] or [parmacist.result/failure]. The default implementation delegates to [fetch-async].

fetch-sync clj/s multimethod

Fetch a source synchronously. This method is dispatched on the :pharmacist/data-source/id key of the source. If no :pharmacist.data-source/fn or :pharmacist.data-source/async-fn is provided, and [fetch] is not implemented for the id, then this method is called with a single source. It should return a [parmacist.result/success] or [parmacist.result/failure].

id clj/s

(id {:pharmacist.data-source/keys [id fn async-fn]})

Return the id of the provided source. Returns the :pharmacist.data-source/id key if set, otherwise makes an effort to infer the id from either :pharmacist.data-source/fn or :pharmacist.data-source/async-fn, whichever is set. If you don't want to manually assign ids, it is strongly recommended that :fn/:async-fn is set to vars, not function values, as Pharmacist will be better able to infer function names.