nwebb » Using Cairngorm & Thoughts On Handling Those Pesky Singletons - The Diigo Meta page

• 12 Jun 08
  

  Mairon Croes

  flex development designpatterns framework cairngorm prana articles blogposts tipsntricks

  • The main reason people tell me they dislike Cairngorm is due to its over-reliance on the Singleton design pattern, and I understand.
  • Singletons increase coupling between classes and make them difficult to unit test. Any class which retrieves a singleton instance becomes unnecessarily coupled to the fact that the class is a singleton - it treats it in a different manor from other classes (i.e. it uses an uncommon instantiation technique). Singletons can't be substituted without changing the source of the class which uses it, nor can they be swapped-out for an interface, because singleton instances are retrieved/instantiated with a call to a static method ( getInstance() by convention ) and you can't have a static method on an interface. This limits polymorphism, going against the OO maxim "Program to an interface, not an implementation".
• 12 Apr 08
  

  ian mcdonald

  Coupling can be reduced across multiple classes if we address the instantiation aspect of singletons.

  flex cairngorm

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