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A Javascript class system in 100% Clojurescript

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# <img align="right" src="https://raw.github.com/bodil/pylon/master/pylon.gif"> 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

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.

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