json

February 27, 2024

I have been in the process of learning a new database. Boy are these interesting.

I have been able to save data using a multimethod!

(defmulti save (fn [game db-type] db-type))

(defmethod save :edn [game db-type]
  (->> game
       (swap! log-edn assoc (:game-id game))
       pr-str
       (spit "log.edn")))

(defmethod save :json [game db-type]
  (->> game
       (swap! log-edn assoc (:game-id game))
       json/write-str
       (spit "log.json")))

This is quite useful and pretty amazing.

Now the interesting part has been retrieving the data. From what I have collected it is not so easy to retrieve the exact data that was placed in JSON. This makes things complicated.

Initially I assumed it would be data in is the data out.

(defmulti fetch-the-games (fn [db-type] db-type))

(defmethod fetch-the-games :edn [_db-type]
  (let [log-edn (slurp "log.edn")]
    (if (empty? log-edn) {} (edn/read-string log-edn))))

(defmethod fetch-the-games :json [_db-type]
  (let [log-json (slurp "log.json")]
    (if (empty? log-json) {} (json/read-str log-json :key-fn keyword))))

So I created this multimethod to retrieve the data. Let me show you what this brings back.

(json/write-str {:a 1 :b 2})
;;=> "{\"a\":1,\"b\":2}"

(json/read-str "{\"a\":1,\"b\":2}")
;;=> {"a" 1, "b" 2}

(json/read-str "{\"a\":1,\"b\":2}"
               :key-fn keyword)
;;=> {:a 1, :b 2}

Upon seeing this I believed I found the way to get my precious data completely. However if you save something like {:a :example :b :example2} and use the :key-fn keyword, you will receive back `{:a “example” :b “example2”}.

Alas I am still at this point. Hopefully soon I will be able to overcome this obstacle and continue playing Tic Tac Toe.

Best,

Merl