NAME

Package::Base - An abstract base for implementation classes to inherit from

SYNOPSIS

            

              
              
#don't use this module directly, but rather inherit from it.
package My::Package;
use base qw(Package::Base);
#define a couple of get/setters
sub slot1 {
  my($self,$val) = @_;
  $self->{'slot1'} = $val if defined($val);
  return $self->{'slot1'};
}
sub slot2 {
  my($self,$val) = @_;
  $self->{'slot2'} = $val if defined($val);
  return $self->{'slot2'};
}
package main:
my $object = My::Package->new(slot1 => 'value1', slot2 => 'value2', slot3 => 'value3');
#slot3 => 'value3' is silently ignored
$object->slot1; #returns 'value1'
$object->slot2; #returns 'value2'
$object->slot3; #error, method undefined
            
          

DESCRIPTION

Package::Base is an abstract base class, meaning it isn't intended to be used directly, but rather inherited from by an instantiable class. In fact, attempting to instantiate a Package::Base object directly will result in an error.

Q: So why would you want to inherit from Package::Base?

A: Because it provides some nice functionality:

* a built-in new() method that does instantiation of a hash based object

* new() accepts an anonymous hash as arguments (a list of key/value pairs, essentially). and sets attributes appropriately within your object if methods of the same name as the keys are found.

* Package::Base::Devel is a subclass specifically designed for debugging Perl classes is bundled with Package::Base, and the inherited interface works the same way. This means that while developing/debugging a module, you can do:

            

              
              
package My::Package;
use base qw(Package::Base::Devel);
#...
            
          

and have nice Log::Log4perl logging about what your method is doing sent to a file, filehandle, email, database... whatever (see Log::Log4perl for details about this amazing logging API). Then, when you're ready to ship, just change the line:

            

              
              
package My::Package;
-use base qw(Package::Base::Devel);
+use base qw(Package::Base);
            
          

and the heavy debugging toll paid for the debug logging vanishes.

* Package::Base comes with a pstub, a drop-in replacement for h2xs if you're writing a module that doesn't rely on Perl XS or C files.

Now to be "fair and balanced" :)

Q: Why might Package::Base not be right for me?

A: It does some things you might not like for stylistic reasons:

* Package::Base currently only works for hash-based objects. This may be extended to support array-based objects in the future.

* Package::Base assumes you have methods overloaded to act as accessors/mutators. e.g. calling $obj-foo(1)> sets object's foo attribute to 1, and calling $obj-foo()> retrieves object's foo attribute's value. See Class::Accessor for an easy way to set these up.

* Package::Base tries to initialize slots for all passed key/value pairs, instead of allowing the constructor, new(), to filter out only those it wants. Class::Base allows filtering like this.

AUTHOR

Allen Day, <allenday@ucla.edu>

SEE ALSO

For another way to do it, see Class::Base.

Class::Accessor.

METHODS

new()

            

              
              
Usage   : This is an abstract constructor, and can't be called directly.
          Use it by either calling it from your subclass directly, e.g.:
          package My::Class;
          use base qw(Package::Base);
          sub new {
            my($class,%arg) = @_;
            my $self = $class->SUPER::new();
            return $self
          }
          or by not declaring a new() method at all, and letting your class
          inherit the new() method at object construction time.
Function: Provides universal construction for hash-based objects.
Returns : An object reference of the calling class, or undef if an attempt is made
          to instantiate Package::Base directly.
Args    : an anonymous hash of object attribute/value pairs.  L</init()>.
            
          

init()

            

              
              
Usage   : $object->init(key1 => 'value1', key2 => 'value2');
Returns : a reference to the calling object
Args    : an anonymous hash of object attribute/value pairs.
Function:
            
          

a method to initialize a new object. Package::Base::init() provides the following functionality:

1. treats arguments as an anonymous hash, and calls set-type methods if possible for each key/value pair. Consider the following code:

            

              
              
package My::Class;
use base qw(Package::Base);
sub meth { my($self,$arg) = @_;
  $self->{'foo'} = $arg if defined($arg);
  return $self->{'foo'}
}
package main;
my $foo = My::Class->new(meth => 'some value');
print $foo->meth(); #prints "some value"
            
          

If method meth() was not defined in My::Class, or any of My::Class's superclasses, the key/value pair is silently ignored. Take advantage of this method as well as any custom initialization you need in your subclass like this:

            

              
              
package My::Class;
use base qw(Package::Base);
sub init {
  my($self,%arg) = @_;
  $self->SUPER::init(@_);
  # now do your stuff
}
            
          

SWAP-IN/OUT METHODS FOR Package::Base::Devel

these methods allow the interchangeable usage of Package::Base and Package::Base::Devel. They're essentially no-op methods.

log()

returns a singleton instance of an object that accepts Log::Log4perl::Logger calls (any calls, actually, it ISA Autoloader), but does nothing with them.

loglevel()

method to support swapability of Package::Base and Package::Base::Devel. returns 1

logconfig()

method to support swapability of Package::Base and Package::Base::Devel. returns 1

cpanm Package::Install

perl -MCPAN -e shell
install Package::Install