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Clojure Object System

A simple, thread-safe, single-inheritance OOP system in Clojure

Leiningen - [cljos "1.3.0-SNAPSHOT"]

Why this heresy?

Clojure is a brilliant functional language, and it would be best to use it as such, but when you just have to write OO code and don't want to give up other benefits that Clojure provides, CljOS might prove to be pretty useful. To read a more detailed write-up, go here.

Usage

Here's a Stack implemented in CljOS:

(defclass <Stack> <Obj>
  {:seq '(), :size 0}
          
  {:init (fn [this size]
           (this :set :size size))
   
   :push (fn [this x]
           (if (< (this :seq count) (this :size))
             (this :setf :seq conj x)
             (throw (Exception. "Stack full!"))))
   
   :pop  (fn [this]
           (if (> (this :seq count) 0)
             (let [x (this :seq first)]
               (this :setf :seq pop)
               x)
             (throw (Exception. "Stack empty!"))))})

which can be used in the following manner:

(def s (new+ <Stack> 3))
(s :state)  ;=> {:seq (), :size 3}
(s :push 1) ;=> {:seq (1), :size 3}
(s :push 2) ;=> {:seq (2 1), :size 3}
(s :push 3) ;=> {:seq (3 2 1), :size 3}
(s :pop)    ;=> 3
(s :state)  ;=> {:seq (2 1), :size 3}

though it would be better to use the doto+ macro:

(doto+ (new+ <Stack> 3)
  (:push 1)
  (:push 2)
  (:push 3)
  :pop :state)  ;=> {:seq (2 1), :size 3}

Note

• :setf stands for 'set with fn' and updates the given var.
• :state can be used to get the object in the form of a Clojure data structure. No serialization required!
• :swap works like swap!, and updates the :state.
• :type gets the name of the class of the object.
• :super can be used to access the super-class's methods, including :init.
• All objects are automatically thread-safe!

License

(C) Divyansh Prakash. CljOS is released under the EPL 1.0 license.