Fix Scoping in CoffeeScript

fixscoping.coffee

# While coffee script offers a "class" keyword, methods still aren't that closely
# associated with class instances. Include fixScoping(this) at the beginning 
# of all of your constructors to make that class' methods well behaved by javascript standards

fixScoping = (instance) ->
    for property, value of instance
        do (property, value) -> #b/c javascript
            if typeof value is "function"
                instance[property] = (args...) -> value.apply(instance, args)

# obligatory contrived arithmetic-based example
class Adder
    constructor: (@amount) -> fixScoping this
    add: (num) -> num + @amount

addTwo = new Adder(2)

[1, 2, 3].map(addTwo.add) # => [3, 4, 5]
# "add" is still bound to its instance, none of that javascript-y silliness here.