match-set-and-get

Convenience macros for messing with Clojure type definitions.

Usage

Currently there's only one macro here called with-setters. with-setters will create a protocol and reify it per mutable field in the type definition.

(with-setters
  (deftype Thinger [^:unsynchronized-mutable thing immutable-thing]))

(def t (->Thinger "hi" "there"))

(set-thing t "bye")

Motivation

I created with-setters because one can only call set! at the top-level of a type's method, not inside a lambda (they don't get closed over). This does not work:

;; From Clojuredocs.org
;; does not work.
(deftype Test [^:unsynchronized-mutable x]
    ITestProtocol
    (act [this] (fn [o] (set! x o))))

If you're trying to create a perforamnt game in CLJS, this is tricky since JS land loves to lean on 'callbacks'.

One way around this limitatiton is to create a setter method for the other methods to call. As you can imagine, it's annoying to try and create a separate protocol with setters for each mutable field in a type definition. I reckon this was done for a good reason, so use this macro if you understand that you actually need mutable fields across your type definition.