On 12/4/05, Ovid <[EMAIL PROTECTED]> wrote:
> "strict::can" is a module which, if used, imports a "can" method into
> your namespace. This version of can() will not report imported helper
> functions or "private" methods. Full docs below.
>
> Comments and suggestions welcome.
I think that the "ignore private" feature is less than useful. If
one agrees with the convention of prepending private methods with an
underscore (which I personally do find useful), then one won't *call*
can() on such a method. But since that convention is not enforced by
the language, what is the value of codifying it in a module?
As to the imported-subroutines feature, that could break a lot of
code. Here's a simple example:
package Foo;
use Exporter;
use strict::can;
if (Foo->can('import')); # BOOM
I can provide other examples from my own code, but I think you get
the point.
The module is clever, but it's not clear to me that it's
practically useful. Could you provide a real-world example where this
would help to prevent or detect a programming error?
- Kurt
> Cheers,
> Ovid
>
> --
>
> NAME
> strict::can - Make can() ignore private methods and imported
> subroutines
>
> VERSION
> Version 0.01
>
> SYNOPSIS
> package Foo;
> use strict::can;
> use HTML::Entities qw(encode_entities); # imported into Foo::
>
> sub new { bless {}, shift }
> sub _private { 'some private function' }
>
> # later
> Foo->can('new'); # true
> Foo->can('encode_entities'); # false (because it's an imported
> function)
> Foo->can('_private'); # false (because it's a private
> function, even
> # though we can still call
> it)
>
> EXPORT
> This module exports a "can()" method into your namespace.
>
> DESCRIPTION
> This module gives your classes a "can()" method which overrides
> (not
> replaces) "UNIVERSAL::can". In most respects it behaves like you
> expect
> it should, but does not report private methods (see below) or
> imported
> functions.
>
> Imported functions
> Frequently we import helper functions into our namespace.
> Ordinarily
> "can()" will return the code reference for these functions even
> though
> this is probably not what we want. "strict::can" will return false
> for
> any imported functions/methods. If you want to expose them, write
> wrapper methods for them.
>
> {
> package Foo;
> use strict::can;
> use HTML::Entities qw/encode_entities/; # import into Foo::
> ...
> sub encode {
> my ($self, @args) = @_;
> return encode_entities(@args);
> }
> }
>
> # later
> if (Foo->can('encode_entities')) {
> # never gets to here
> }
>
> Private methods
> Methods which begin with an underscore are, by convention,
> considered
> "private" and should not be relied on. Unfortunately, "can()"
> succeeds
> with those, too. "strict::can" will return false for private
> methods
> unless the class checking "can()" is a *subclass* of the class or
> instance it is checking. This is because we're allowing a little
> more
> trust for subclasses as "private" methods are often "protected"
> methods
> which subclasses should be allowed to use.
>
> {
> package Foo;
> use strict::can;
> ...
> sub _private {
> return 'Top Sekret!';
> }
> }
>
> # later
> {
> package main;
> if (Foo->can('_private')) {
> # never gets to here
> }
> }
> {
> package Foo::Bar;
> our @ISA = qw(Foo);
> if (Foo->can('_private')) {
> # success at last!
> }
> }
>
> AUTHOR
> Curtis "Ovid" Poe, "<[EMAIL PROTECTED]>"
>
> BUGS
> Please report any bugs or feature requests to
> "[EMAIL PROTECTED]", or through the web interface at
> <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=strict-can>. I will
> be
> notified, and then you'll automatically be notified of progress on
> your
> bug as I make changes.
>
> SEE ALSO
> The "B::svref_2object" function.
>
> COPYRIGHT & LICENSE
> Copyright 2005 Curtis "Ovid" Poe, all rights reserved.
>
> This program is free software; you can redistribute it and/or
> modify it
> under the same terms as Perl itself.
>
> --
> If this message is a response to a question on a mailing list, please send
> follow up questions to the list.
>
> Web Programming with Perl -- http://users.easystreet.com/ovid/cgi_course/
>
