dynamic-record.clj

(defn dynamic-record [base-name field-names & init-values]
  (let [klass (eval `(defrecord ~(gensym base-name) ~(vec field-names)))
        ctor (first (.getConstructors klass))
        vals (take (count field-names)
                   (concat init-values (repeat nil)))]
    (.newInstance ctor (into-array Object vals))))

(dynamic-record "MyRecord" '(foo bar) :foo)

;; -> #:user.MyRecord14544{:foo :foo, :bar nil}