Ruby-ism: include/extend

[jnicklas]

Yay classes! Maybe we could have Ruby's extend/include to mix in stuff in our classes? We can make it way cooler than Ruby by allowing any Object to be mixed in!

nameMixin: { name: 'Steve' }
makeSteveMixin: { steve: -> new this() }
class Person
  include nameMixin
  extend makeSteveMixin

steve: new Person
steve.name() #=> 'Steve'
steve2: Person.steve

[tim-smart]

Well technically they aren't 'classes', rather just a wrapper around Javascript prototypes.

One question one must ask, is how far are we wanting to take 'classes' in Coffee. We don't want to bending the underlying Javascript too much...

[jashkenas]

So, you already have this ability in JavaScript. Here's extend:

extend: (obj, mixin) ->
  for name, method of mixin
    obj[name]: method

And here's include, using extend from above:

include: (klass, mixin) ->
  extend klass.prototype, mixin

It's all just attaching functions to the proper location. I don't think that we need to formalize this pattern in CoffeeScript, as many core libraries (jQuery, Prototype, Underscore) already have this extend function, and many objects that are intended for use as mixins already have it built-in. Any many people prefer helper objects and composition over mixing methods right in to the prototype.

So, closing as a 'wontfix'.

But if you use the methods above, your example could be written like so:

nameMixin: { name: 'Steve' }
makeSteveMixin: { steve: -> new this() }
class Person

include Person, nameMixin
extend Person, makeSteveMixin

steve: new Person()
puts steve.name
steve2: Person.steve

This runs, and prints "Steve".

[petebrowne]

If you'd like to use this feature, I've built a simple class for including mixins: Mixable.

With it, you get pretty damn close to extend and include keywords:

nameMixin = { name: "Steve" }

makeSteveMixin = { steve: -> new this() }

class Person extends Mixable
  @include nameMixin
  @extend  makeSteveMixin

steve = new Person
steve.name() # => "Steve"
steve2 = Person.steve()