Hm, I am not a student of OOP theory, but I find that "most of what Moo faciliates" is not so much in the instance constructor but in attribute declarations, of which I typically have many times more than constructor params. I find that triggers, clearers, predicates and lazy builders etc. are among the main features of the framework, and they are for all attributes declared.

I don't normally find a problem with having a RO "accessor" derived from declaring an attribute in order to take a named constructor param, but if you really don't want its value to be available to consumers you could maybe do something with BUILDARGS?

package Foo {
    use Moo;

    has qux => (is => 'ro');

    around BUILDARGS => sub {
        my ($orig, $class, $args) = @_;
        return {
            qux => $args->{bar} * $args->{baz},
        };
    };
};

use strict;
use warnings;
use feature 'say';

my $o = Foo->new({
    bar => 6,
    baz => 7,
});

say $o->qux;
say $o->bar;

[download]
Output: 
$ perl 11107488.pl

42
Can't locate object method "bar" via package "Foo" at 11107488.pl line
+ 24.

[download]

Hope this helps!


The way forward always starts with a minimal test.

In reply to Re^4: If Perl 5 were to become Perl 7, what (backward-compatible) features would you want to see? by 1nickt
in thread If Perl 5 were to become Perl 7, what (backward-compatible) features would you want to see? by haukex

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