Clojure：将值设置为键

Question

May be, it is a stupid question, but it may help many of newbies. How do I add a key-value pair to the map?

I mean something like:

(defn init-item [v item]
  (let [{:keys [id value]} item]
    (-> v
        (assoc :{ID_AS_A_KEY} value))))

And I get:

(init-item {} {:id "123456789" :value [:name "King" :surname "Leonid"]})
user=> {:123456789 [:name "King" :surname "Leonid"]}

Answer 1

Just don't do it. Use the string itself as your map key. There's no reason to make it a keyword. It's much easier to work with if you leave it alone.

(defn init-item [v item]
  (assoc v (:id item) (:value item)))

Answer 2

I think this is what you meant to do:

  (defn init-item
    [dest-map item]
    (let [item-id-str (:id item)
          item-val    (:value item)
          item-id-kw  (keyword item-id-str)]
      (assoc dest-map item-id-kw item-val)))

  (let [all-items {:a 1 :b 2 :c 3}
        item-1    {:id    "123456789"
                   :value [:name "King" :surname "Leonid"]}]

(init-item all-items item-1)  
  ;=>  {:a 1, :b 2, :c 3, :123456789 [:name "King" :surname "Leonid"]}

Clojure has functions name , symbol , and keyword to convert between strings and symbols/keywords. Since you already have the ID as a string, you just need to call keyword to convert it.

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