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Re: Design Patterns

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On 2/5/13 5:34 PM, Arne Vajhøj wrote:
> On 2/4/2013 11:10 PM, Stefan Ram wrote:
>> Arne Vajhøj <arne@vajhoej.dk> writes:
>>>> Pattern or anti-pattern, I never encountered a situation where I felt a
>>>> need for »singletons«.
>>> Other have.
>>
>>    Maybe someone can come up with an SCSE where a singleton is needed.
>
> Needed as in "problem can not be solved without"? I doubt such exist!
>
> Needed as in "a large of programmers prefer it to solve the problem"?
> There are many. Connection pools, configuration settings, web app
> statistics etc..

Logging is another one.  They thing about all those is that there is a 
globally accessible shared instance, but that doesn't have to be 
enforced by the class itself. Rather, the life-cycle of the object is 
managed externally.

Self-managed life-cycles should be very rare.  For instance, something 
which actually manages external resources may need to enforce some 
invariants about its life-cycle, in order to manage external state in a 
sane manor.  This isn't something an application programmer need worry 
about on a frequent basis.

I'm *not* a fan of a global Configuration object for many reasons.  One 
is that the configuration class becomes overly involved with the rest of 
the application.  At least, if they treat it as a place to "go grab some 
settings".  If the settings are injected, then that's a different story.

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Design Patterns dougmmika@gmail.com - 2013-02-02 16:17 -0800
  Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 19:39 -0500
    Re: Design Patterns Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-02-03 18:52 +0100
      Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-03 14:23 -0800
      Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:57 -0500
        Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 11:10 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-09 19:36 -0500
            Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:44 -0800
              Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:47 -0800
                Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-10 12:28 -0500
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:35 -0500
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:36 -0500
                Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-10 23:12 -0800
          Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-09 19:45 -0500
  Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 20:17 -0500
  Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 19:43 -0800
    Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-02 20:54 -0800
      Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 21:11 -0800
        Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-03 08:24 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:41 -0500
    Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-02 21:57 -0800
  Re: Design Patterns Roedy Green <see_website@mindprod.com.invalid> - 2013-02-03 06:38 -0800
  Re: Design Patterns Joerg Meier <joergmmeier@arcor.de> - 2013-02-04 17:06 +0100
    Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 12:38 -0800
    Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:31 -0500
      Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-04 21:03 -0800
        Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 21:25 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:54 -0500
            Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 17:51 -0800
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:54 -0500
        Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-05 09:43 +0000
          Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:03 -0800
            Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:09 -0500
          Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 13:56 -0800
            Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 14:30 -0800
            Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-05 14:33 -0800
            Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-06 09:03 +0000
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:07 -0500
      Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 09:10 -0500
        Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 13:20 -0500
          Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:10 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:11 -0500
      Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-05 09:53 -0800
        Re: Design Patterns Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-05 20:17 -0400
        Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:50 -0500
      Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:34 -0500
        Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-06 08:40 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:38 -0500
    Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:41 -0500

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