Re: Singletons

From: Ilja Preuß (it_at_iljapreuss.de)
Date: 01/19/05

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    Date: Wed, 19 Jan 2005 19:40:13 +0100

    Thomas Gagne wrote:

    > People abuse getters and setters? They must be evil and avoided.

    Well, I do use getters and setters. But I also find that when I think about
    alternative designs that don't need them, I regularly come up with better
    designs.

    > People abuse singletons? They must be evil and avoided.

    It's not just that people abuse singletons. It's that I can't see many
    reasons to use one.

    > People abuse gotos? casts? void *? char *?

    The latter must come from a language I'm not literate enough in to comment,
    but I'm quite sure that it pays off to at least be suspicious of gotos and
    casts.

    > People may call functions you've documented as "insiders-only"? Make
    > them private and don't let them.
    > People may override a method you don't think they should?
    > People may add a function to your precious class you didn't think of?
    > Make it so they can't. Make your intentions so ironclad that no one
    > can do anything other than what you intended to be done the way you
    > intended it should be done.

    Well, I actually find it to be quite usefull from time to time to have those
    language features at my disposal when I later can undo that decision by
    changing the code. I agree, though, that it tends to criple an API that you
    can't change.

    > Just because a programmer may trip themselves up is a poor excuse to
    > language design.

    And that's exactly a reason *not* to use a Singleton. Just because currently
    you only want to have one instance and fear that someone might trip himself
    by creating a second one is a bad excuse for cripling a class by not
    allowing more than one instance, and coupling the whole system to that
    decision so that it later gets a real pain to change!

    Cheers, Ilja

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