Indeed it is fun. I love the language and now with Inline::Perl5 the number of projects I'm willing to try it out on is greatly increased!

Thanks for all your research and link to proxys. Indeed, it looks like these can save us if we were to create a class with a publicly writable attribute which really should have been implemented as a method. And, indeed there do seem to be bugs lurking still. I can't quite get it to work now, but am sufficiently satisfied that something like this will eventually:

class Interval {
    has Real $.lb = die 'Lower bound is required';
    has Real $.ub = die 'Upper bound is required';

    method lb() is rw {
        return Proxy.new:
            FETCH => method () { return $!lb; },
            STORE => method ($lb) {
                die "Require lb <= ub" unless $lb <= $!ub;
                $!lb = $lb;
            };
    }

    method ub() is rw {
        return Proxy.new:
            FETCH => method () { return $!ub; },
            STORE => method ($ub) {
                die "Require lb <= ub" unless $!lb <= $ub;
                $!ub = $ub;
            };
    }
}

[download]

Good Day,
    Dean

In reply to Re^2: [perl6] Complex Attribute Validation and/or Triggers by duelafn
in thread [perl6] Complex Attribute Validation and/or Triggers by duelafn

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.