I see your point about classwide methods on a package being a singleton, the class itself being like a single instance with lexical member variables.

In practice, though, I have found that classwide methods make it hard to replace functionality by subclassing, because one needs to hardcode the package name everywhere its methods are called. Then, when subclassing the singleton package, one needs to replace all those calls to instead use the name of the subclass. Do you know if there's a way around this?

I think this is a shortcoming of using classwide methods. Where I work we now instead favor having Factory classes for producing singleton variables that we make available as "framework globals" as described in my earlier posting. This Factory class reads a configuration file in order to determine what kind of subclass it should instantiate, which works great for plug-and-play configuration of different installs of our application. Example: 

 

$FOO = FooFactory->get_foo();

[download]
As a convention we use all-caps for singleton variables.

In reply to Re: •Re: Avoiding global object handle by gregorovius
in thread Avoiding global object handle by Biker

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.