CoffeeScript Singleton base class

gistfile1.coffee

singletonCheck = {}

class Singleton
  @getInstance: -> @instance ?= new @ singletonCheck

  constructor: (check) ->
    if check isnt singletonCheck
      throw new Error "Singleton must be instantiated with getInstance()"
      return
    console.log "Singleton", "init"
    @init?()


class MySingletonClass extends Singleton
  init: ->
    console.log "MySingletonClass", "init"


MySingletonClass.getInstance() # OK
new MySingletonClass() # Error