This is a nice way to force instantiation in a Coffeescript "class". It basically allows it to look like a function. Adapted from John Resig's blog post http://ejohn.org/blog/simple-class-instantiation/

gistfile1.coffee

class Foo
  constructor: ->
    return new Foo() unless @ instanceof Foo
    
    # Guaranteed to be an object here
    @announce()

  announce: -> console.log "here!"

# These are equivalent now
Foo()
new Foo()

gistfile2.coffee

# If you want to apply the arguments to the instantiated object,
# you have to do something like this.
class Foo
  constructor: ->
    if @ instanceof Foo
      console.log arguments
    else
      FooInstance = ->
      FooInstance:: = Foo::
      instance = new FooInstance()
      obj = Foo.apply(instance, Array.prototype.slice.apply(arguments))
      return if Object(obj) is obj then obj else instance

# These are the same
Foo(1, 2, 3)
new Foo(1, 2, 3)