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https://github.com/bodil/pylon

A Javascript class system in 100% Clojurescript
https://github.com/bodil/pylon

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A Javascript class system in 100% Clojurescript

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README 

        
#  Pylon



A Javascript class system in 100% Clojurescript.



## Rationale



Class based OO is not cool. In fact, it's quite the opposite of the

kind of code you should be writing as a Clojurescript developer.

However, you sometimes find yourself having to deal with Javascript's

ecosystem—certain of its more popular libraries in particular—out of

necessity. Clojurescript's core interop facilities are fine for

dealing with dumb JS objects, but when you have to get into more

advanced OO—creating classes and subclasses—the primitives are no

longer adequate.



Pylon is intended as an interop facility. It is most emphatically not

intended as a tool for turning Clojurescript into an OO language.

Don't build your applications on it; be smart and use functional

programming instead. Pylon is only for when you really need to deal

with legacy Javascript code.



## Installation



To use Pylon in your project, put the following in the `:dependencies`

vector of your `project.clj` file:



```clojure

[org.bodil/pylon "0.3.0"]

```



## Defining Classes



Use the `defclass` macro to build Javascript style classes using Pylon.



```clojure

(ns pylon.test

  (:require [pylon.classes])

  (:use-macros [pylon.macros :only [defclass]]))



(defclass Hello

  (defn constructor [name]

    (set! @.name name))

  (defn hello []

    (console/log (str "Hello " @.name "!"))))



(.hello (Hello. "Kitty"))

;; => "Hello Kitty!"

```



Note that all methods have a `this` symbol available to them, just

like in Javascript. Unlike in Javascript, it will always be bound to

the actual object instance, even when passing an instance method as a

callback.



Notice the shorthand for referencing object properties: `@.name`

anywhere inside a `defclass` is synonymous to `(.-name this)`. Thus,

to read a property `foo` on the current object, simply use `@.foo`,

and to set the property, use `(set! @.foo value)`. If `foo` is a

method, you can invoke it directly using `(@.foo)`, or with arguments,

`(@.foo "bar" "gazonk")`. (Note that this only works reliably on Pylon

methods, as Clojurescript will clobber `this` when a function is

called in this way.)



## Inheritance



Pylon allows you to define inheritance using the `:extends` keyword,

and call superclass methods using the `super` macro.



```clojure

(ns pylon.test

  (:require [pylon.classes])

  (:use-macros [pylon.macros :only [defclass super]]))



(defclass Hello

  (defn constructor [name]

    (set! @.name name))

  (defn hello []

    (console/log (str "Hello " @.name "!"))))



(.hello (Hello. "everypony"))

;; => "Hello everypony!"



(defclass HelloSailor :extends Hello

  (defn constructor []

    (super "sailor")))



(.hello (HelloSailor.))

;; => "Hello sailor!"

```



## Mixins



If you need multiple inheritance, you can use the `:mixin` keyword to

extend your prototype further. Note that we've left the world of

prototypal inheritance behind when we do this: properties are copied

from the mixin objects into your object prototype; it does not

actually add more parent prototypes, which would be impossible.



# License



Copyright 2012 Bodil Stokke



Licensed under the Apache License, Version 2.0 (the "License"); you

may not use this file except in compliance with the License. You may

obtain a copy of the License at

[http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0).



Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or

implied. See the License for the specific language governing

permissions and limitations under the License.