How to keep a list of objects in Clojure?

Question

I'm trying to use java interop, to create a list of objects.

I have tried for and doseq, and they both have problems.

for is lazy, and I need to create all the objects, as they interact with each other internally.

(def master-object (MasterObject.))

(for [x [1 10 50 99]]
  (let [child (.createChildObject master-object)]
    (.setCoefficient child x)
    child))

doseq creates all, but don't return a list.

(doseq [x [1 10 50 99]]
  (let [child (.createChildObject master-object)]
    (.setCoefficient child x)
    child))

I was thinking about using loop and recur, but was wondering if could be a more idiomatic way of doing that.

Thanks

Answer 1

If you need to create all the objects then I think it would be idiomatic to return a vector rather than a list, for example:

(vec (for [x (range 3)]
       x))

There are a few different ways to force all the output from a for. The above is one of them. vec is just short for into []. So if you definitely need a realised list you could instead:

(into '() (for [x (range 3)]
            x))

For creating a list of objects doseq will not help you as it is only about 'side effects'.

Really you could look at using map for what you want to accomplish. Make a separate mapping function and map over it:

(defn make-child [x]
  (let [child (.createChildObject master-object)]
      (.setCoefficient child x)
      child))

(map make-child [1 10 50 99])