Singleton Pattern on Coffeescript

Singleton definition:

class Singleton
 @getInstance: ->
 @_instance ?= new @(arguments...)

Our singleton class:

class Manager extends Singleton
 constructor: (arg) ->
 @arg = arg

First call, initialize it.

manager = Manager.getInstance("hello")
console.log(manager.arg) # hello

Second call, just return the instance.

manager = Manager.getInstance("world")
console.log(manager.arg) # hello

#design patterns

#singleton

#coffeescript

Written by Endel Dreyer

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4 Responses

Add your response

jamesw

You'd need to add additional code in a constructor for Manager to ensure there is only one instance or that getInstance is always used.

over 1 year ago ·

SamirTalwar

The idea that people are adding new singletons to their code is something that worries me greatly.

over 1 year ago ·

endel

@SamirTalwar ok, share what you think it's right instead

over 1 year ago ·

pbihler

What about this approach:

 class Singleton
 @getInstance: ->
 @_instance ?= new @(@,arguments...)

 constructor: (args...) ->
 unless @constructor == args.shift()
 throw new Error('Cannot call new on a Singleton')
 return args


class Manager extends Singleton
 constructor: ->
 [@arg] = super

It makes new Manager() unlikely.

over 1 year ago ·