CODEWITHSUNDEEP
dictionaryclojurestandard-library
haijin
haijin

Reputation: 948

what is the idiomatic way to slice a map in Clojure?

For lists and vectors, we can slice the sequence and take any portion we want. How to do similar operations to map objects ?

For example, I have a list of map object,

(def plays [
        {:name "Burial",     :plays 979,  :loved 9}
        {:name "Eno",        :plays 2333, :loved 15}
        {:name "Bill",       :plays 979,  :loved 9}
        {:name "Magma",      :plays 2665, :loved 31}])

For each map, I want to slice off plays column, and add rate column with default value, what is the idiomatic way to do this ?

Upvotes: 6

Views: 863

Answers (2)

mtyaka
mtyaka

Reputation: 8848

Depending on your use-case, you might also find select-keys useful in addition to assoc and dissoc:

clojure.core/select-keys
([map keyseq])
  Returns a map containing only those entries in map whose key is in keys

(select-keys {:name "Eno" :plays 2333 :loved 15} [:name :loved])
;; => {:name "Eno" :loved 15}

Upvotes: 15

Ankur
Ankur

Reputation: 33657

assoc and dissoc are your friends in this case:

(map #(-> % (dissoc :plays) 
            (assoc :rate 10)) plays)

Upvotes: 18

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