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clojure

Is it possible to destructure in case for use in a threading macro?

(def val { :type "bar" })

(-> val
  (case ???
    "bar" "bar type"
    "baz" "baz type"
    "other type"))

I'd like to include a case in a threading macro so I can branch based on one of the keys of val, a hash map. Is this possible?

EDIT: I need to thread val not a key from val as further functions will need the whole of val. I essentially want to branch to a function within the threading macro based on a key of val. But still pass val onward.

Solution

  • Consider using a multimethod dispatch here:

    (defmulti some-operation :type)

(defmethod some-operation "bar"
  [val]
  (println "Bar type!")
  (assoc val :x 42))

(defmethod some-operation "baz"
  [val]
  (println "Baz type!")
  (assoc val :x 100))

(-> {:type "bar"}
    some-operation
    some-other-operation)