Devel::EnforceEncapsulUsernContributed Perl DocuDevel::EnforceEncapsulation(3)NAMEDevel::EnforceEncapsulation - Find access violations to blessed objects
SYNOPSIS
package BankAccount;
sub new {
my $pkg = shift;
return bless {}, $pkg;
}
sub balance {
my $self = shift;
return $self->{balance};
}
# ... etc. ...
package main;
Devel::EnforceEncapsulation->apply_to('BankAccount');
my $acct = BankAccount->new();
print $acct->balance(),"\n"; # ok
print $acct->{balance},"\n"; # dies
LICENSE
Copyright 2006 Clotho Advanced Media, Inc., <cpan@clotho.com>
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
DESCRIPTION
Encapsulation is the practice of creating subroutines to access the
properties of a class instead of accessing those properties directly.
The advantage of good encapsulation is that the author is permitted to
change the internal implementation of a class without breaking its
usage.
Object-oriented programming in Perl is most commonly implemented via
blessed hashes. This practice makes it easy for users of a class to
violate encapsulation by simply accessing the hash values directly.
Although less common, the same applies to classes implemented via
blessed arrays, scalars, filehandles, etc.
This module is a hack to block those direct accesses. If you try to
access a hash value of an object from it's own class, or a superclass
or subclass, all goes well. If you try to access a hash value from any
other package, an exception is thrown. The same applies to the scalar
value of a blessed scalar, entry in a blessed array, etc.
To be clear: this class is NOT intended for strict enforcement of
encapsulation. If you want bullet-proof encapsulation, use inside-out
objects or the like. Instead, this module is intended to be a
development or debugging aid in catching places where direct access is
used against classes implemented as blessed hashes.
To repeat: the encapsulation enforced here is a hack and is easily
circumvented. Please use this module for good (finding bugs), not evil
(making life harder for downstream developers).
METHODS
$pkg->apply_to($other_pkg);
$pkg->apply_to($other_pkg, {policy => 'carp'});
Add strict encapsulation to an existing $other_pkg. The
encapsulation changes only apply to instances created after the
call.
The optional "policy" argument allows you to change the response to
an illegal access. By default the policy is "croak", which invokes
"Carp::croak()". The alternative is "carp" which invokes
"Carp::carp()" instead.
$pkg->remove_from($other_pkg);
Remove any encapsulation previously set by "apply_to()". This does
not affect instances created before this call.
SEE ALSO
Class::Privacy
Class::Privacy is a very similar implementation that is, in general,
stricter than this module. The key differences:
· D::E applies externally post-facto; C::P from inside the code.
· D::E allows access from sub/superclasses; C::P does not
(deliberately!).
· D::E supports all dereferencers from overload.pm; C::P supports
"%", "@", "$", and "&".
· D::E allows access from anything in the same package; C::P allows
access only from matching package AND file.
Inside-out classes
Class::InsideOut, Object::InsideOut and Class::Std are all
implementations of "inside-out" objects, which offer a stricter
encapsulation style at the expense of a less familiar coding style.
DIAGNOSTICS
"Illegal attempt to access %s internals from %s"
(Fatal) You tried to access a hash property directly instead of via
an accessor method. The %s values are the object and caller
packages respectively.
QUALITY
We care about code quality. This distribution complies with the
following quality metrics:
· Perl::Critic v0.20 passes
· Devel::Cover test coverage at 100%
· Pod::Coverage at 100%
· Test::Spelling passes
· Test::Portability::Files passes
· Test::Kwalitee passes
CAVEATS
The regression tests do not cover blessed code or glob references.
Any other issues:
http://rt.cpan.org/Dist/Display.html?Queue=Devel-EnforceEncapsulation
<http://rt.cpan.org/Dist/Display.html?Queue=Devel-EnforceEncapsulation>
AUTHOR
Clotho Advanced Media Inc., cpan@clotho.com
Maintainer: Chris Dolan
CREDITS
This idea, and the original source code, came from Adrian Howard via
Curtis "Ovid" Poe on
<http://www.perlmonks.org/?node_id=576707|perlmonks.org>. Adrian has
authorized me to release a variant of his code under the Perl license.
Joshua ben Jore provided crucial improvements that simplified yet
generalized the implementation. This module would not be half as
useful without his contributions.
<http://use.perl.org/comments.pl?sid=33253&cid=50863>
Ricardo Signes contributed the "{policy =" 'carp'}> feature (with
tests!). <http://rt.cpan.org/Ticket/Display.html?id=22024>
perl v5.14.1 2006-10-11 Devel::EnforceEncapsulation(3)
