MooseX::Declare and its ilk allow the arguments to a method and (somewhat experimentally) the return value, to be declared in terms of Moose type constraints. A type constraint can use arbitrary code to verify that a value meets it.

  subtype 'SmallInt'
    => as 'Int'
    => where { $_ < 10 };

[download]

It allows the declaration of named parameters, and required and optional parameters.

This seems to meet the "I want something that verifies incoming parameters" part of the quest.

The reason I suggest that it's mostly useful for subs that are intended to be called as methods, rather than as functions, is that the declaration syntax offers certain shortcuts that make the assumption that the first parameter to will be a blessed object, and that the function body will want to refer to it as "$self".

class Person
{
  # ...

  method thank (Person $person)
  {
    # ...
  }

  method accept_gift (Gift $gift)
  {
    $self->push_posession($gift);
    $self->thank($gift->giver);
  }
}

my $me  = Person->new;
my $bob = Person->new;
my $dog = Gift->new(giver => $me, item => Puppy->new);

$bob->accept_gift($dog);         # ok
Person::accept_gift($bob, $dog); # ok
Person::accept_gift($dog);       # dies

[download]

In reply to Re^5: Pre/post subroutine assertions and documentation module? by tobyink
in thread Pre/post subroutine assertions and documentation module? by suaveant

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.