Re: [Rails-devel] Starting on a client/server

[John A. T. <ja...@ja...>]

Erik Vos wrote:
> I consider a class "getInstance()" method to be a perfectly acceptable way
> to get access to the instance of a Singleton. Whether or not singletons are
> a good idea is a different discussion. In general I see no problems with it,
> except that in Rails we should get rid of most existing singletons if we
> want to aim for a multi-game server.
>
> However, I don't understand what you mean with "global variables" in this
> context. And I certainly don't see any connection between variables being
> global (or whatever) and the use of class getInstance methods.
>
> Puzzled,
>   
The argument against singletons is that it makes testing hard, as you 
can't easily replace the underlying object with a mocked instance.  The 
alternative is using dependency injection, such as Guice.

Also see 
http://code.google.com/p/google-singleton-detector/wiki/WhySingletonsAreControversial 
(which is a Google project to help detect various kinds of global state).

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John A. Tamplin					ja...@ja...
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