Class::Data::Accessor(User Contributed Perl DocumentatClass::Data::Accessor(3)NAMEClass::Data::Accessor - Inheritable, overridable class and instance
data accessor creation
SYNOPSIS
package Stuff;
use base qw(Class::Data::Accessor);
# Set up DataFile as inheritable class data.
Stuff->mk_classaccessor('DataFile');
# Declare the location of the data file for this class.
Stuff->DataFile('/etc/stuff/data');
# Or, all in one shot:
Stuff->mk_classaccessor(DataFile => '/etc/stuff/data');
Stuff->DataFile; # returns /etc/stuff/data
my $stuff = Stuff->new; # your new, not ours
$stuff->DataFile; # returns /etc/stuff/data
$stuff->DataFile('/etc/morestuff'); # sets it on the object
Stuff->DataFile; # still returns /etc/stuff/data
DESCRIPTION
This module is now deprecated!
Please consider using Class::Accessor::Grouped or Moose
Class::Data::Accessor is the marriage of Class::Accessor and
Class::Data::Inheritable into a single module. It is used for creating
accessors to class data that overridable in subclasses as well as in
class instances.
For example:
Pere::Ubu->mk_classaccessor('Suitcase');
will generate the method Suitcase() in the class Pere::Ubu.
This new method can be used to get and set a piece of class data.
Pere::Ubu->Suitcase('Red');
$suitcase = Pere::Ubu->Suitcase;
Taking this one step further, you can make a subclass that inherits
from Pere::Ubu:
package Raygun;
use base qw(Pere::Ubu);
# Raygun's suitcase is Red.
$suitcase = Raygun->Suitcase;
Raygun inherits its Suitcase class data from Pere::Ubu.
Inheritance of class data works analogous to method inheritance. As
long as Raygun does not "override" its inherited class data (by using
Suitcase() to set a new value) it will continue to use whatever is set
in Pere::Ubu and inherit further changes:
# Both Raygun's and Pere::Ubu's suitcases are now Blue
Pere::Ubu->Suitcase('Blue');
However, should Raygun decide to set its own Suitcase() it has now
"overridden" Pere::Ubu and is on its own, just like if it had
overridden a method:
# Raygun has an orange suitcase, Pere::Ubu's is still Blue.
Raygun->Suitcase('Orange');
Now that Raygun has overridden Pere::Ubu, further changes by Pere::Ubu
no longer effect Raygun.
# Raygun still has an orange suitcase, but Pere::Ubu is using Samsonite.
Pere::Ubu->Suitcase('Samsonite');
You can also override this class data on a per-object basis. If $obj
isa Pere::Ubu then
$obj->Suitcase; # will return Samsonite
$obj->Suitcase('Purple'); # will set Suitcase *for this object only*
And after you've done that,
$obj->Suitcase; # will return Purple
but
Pere::Ubu->Suitcase; # will still return Samsonite
If you don't want this behaviour use Class::Data::Inheritable instead.
"mk_classaccessor" will die if used as an object method instead of as a
class method.
METHODS
mk_classaccessor
Class->mk_classaccessor($data_accessor_name);
Class->mk_classaccessor($data_accessor_name => $value);
This is a class method used to declare new class data accessors. A new
accessor will be created in the Class using the name from
$data_accessor_name, and optionally initially setting it to the given
value.
To facilitate overriding, mk_classaccessor creates an alias to the
accessor, _field_accessor(). So Suitcase() would have an alias
_Suitcase_accessor() that does the exact same thing as Suitcase().
This is useful if you want to alter the behavior of a single accessor
yet still get the benefits of inheritable class data. For example.
sub Suitcase {
my($self) = shift;
warn "Fashion tragedy" if @_ and $_[0] eq 'Plaid';
$self->_Suitcase_accessor(@_);
}
Overriding accessors does not work in the same class as you declare the
accessor in. It only works in subclasses due to the fact that
subroutines are loaded at compile time and accessors are loaded at
runtime, thus overriding any subroutines with the same name in the same
class.
mk_classaccessors(@accessornames)
Takes a list of names and generates an accessor for each name in the
list using "mk_classaccessor".
AUTHORS
Based on the creative stylings of Damian Conway, Michael G Schwern,
Tony Bowden (Class::Data::Inheritable) and Michael G Schwern, Marty
Pauley (Class::Accessor).
Coded by Matt S Trout Tweaks by Christopher H. Laco.
BUGS and QUERIES
If your object isn't hash-based, this will currently break. My
modifications aren't exactly sophisticated so far.
mstrout@cpan.org or bug me on irc.perl.org, nick mst claco@cpan.org or
irc.perl.org, nick claco
LICENSE
This module is free software. It may be used, redistributed and/or
modified under the same terms as Perl itself. (see
http://dev.perl.org/licenses/artistic.html and
http://www.opensource.org/licenses/gpl-license.php)
SEE ALSO
perltootc has a very elaborate discussion of class data in Perl.
Class::Accessor, Class::Data::Inheritable
perl v5.14.0 2008-08-13 Class::Data::Accessor(3)
