Use REST inside your Clojure programs. Represent an edit to a data structure as a data structure (patch) and apply it to any nested combination of maps, lists, vectors and sets.
Add this to project.clj (if you use Leiningen)
[patcher "0.1.3"]or this to deps.edn (if you don't)
{patcher {:mvn/version "0.1.3"}}First things first, let's get imports and namespaces off our chest.
(require '[patcher.core :refer [apply-patch]])Then fire up the REPL, type a definition in-o:
(def patch {:type :put :path [:some :keys] :value "A new value"})And apply it to a thing-o
(apply-patch patch {:some {:keys "An old value"} :other {:keys "I am a value too, y'know"}})
=> {:some {:keys "A new value"} :other {:keys "I am a value too, y'know"}}Apply it to a thing-o
(apply-patch {:type :post :path [:interests] :value :music} {:age 35 :sex :male :interests [:cooking]})
=> {:age 35 :sex :male :interests [:cooking :music]}A patch is a map with 3 keys: :type, :path and :value. :type can be :put, :post, :delete or :merge.
:put will replace whatever value you would get with (get-in coll path) with value
:post is similar, but it will insert (conj) value into the existing sequence instead of replacing it
:merge assumes that value is a map or a sequence and replaces a map or a sequence at path with a concatenation (merger) of it and value
:delete will purge it from the data structure so that (get-in coll path) returns nil
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