Question

I am a total newbie to clojure and trying to follow some tutorials basically. I have a question about defrecords.

Here is the thing that I am trying to do :

(defrecord somemap [key1 key2 key3 key4])

(defn give-me-map [m1 m2]
  (somemap. m1 m2))

On the code above, i would like to have key3 and key4 as optional, so that i wont need to give values to them each time a create a somemap object.

there is a similar question here, but it does the reverse of what i am trying to do here.

So the is it possible to define defrecord with optional fields?

Answer 1

When you use (defrecord T [...]), two factory functions are created: ->T and map->T.

The first uses the positional parameters as keys. The second applies an arbitrary map to the record.

You can keep key3 and key4 in the constructor and use map->somemap.

(defrecord somemap [key1 key2 key3 key4])

(defn give-me-map
  [key1 key2]
  (map->somemap {:key1 key1 :key2 key2}))