CODEWITHSUNDEEP
clojure
bpereira
bpereira

Reputation: 1016

Using swap! instead of reset! in atom - clojure

Given I have this action to perform

(def structure (atom [{:id "an-id"} {:id "another-id"}]))
(def job {:type "some-job"})

(reset! structure (map #(if (= "an-id" (:id %)) (update-in % [:performed-jobs] (fnil conj []) job) %) @structure))

next structure:
[{:id "an-id" :performed-jobs [{:type "some-job"}]} {:id "another-id"}]

How can I use swap! to change a single occurrence in my structure instead of resetting it all?

Upvotes: 1

Views: 349

Answers (1)

Michiel Borkent
Michiel Borkent

Reputation: 34800

  1. Replace reset! by swap! by giving it a function that takes the old value of the atom and returns a new value to store in the atom.

  2. Replace dereferencing of the atom with the function's argument, the old value.

    (swap! structure
  (fn [old]
    (map #(if (= "an-id" (:id %))
            (update-in % [:performed-jobs]
                       (fnil conj []) job) %)
          old)))

Upvotes: 1

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