NAME
    Class::Member - A set of modules to make the module developement easier

SYNOPSIS
     package MyModule;
     use Class::Member::HASH qw/member_A member_B -CLASS_MEMBERS
                                -NEW=new -INIT=init/;
     
 or
     
 package MyModule;
     use Class::Member::GLOB qw/member_A member_B -CLASS_MEMBERS
                                -NEW=new -INIT=init/;
     
 or
     
 package MyModule;
     use Class::Member qw/member_A member_B -CLASS_MEMBERS/;
     
 or
     
 package MyModule;
     use Class::Member::Dynamic qw/member_A member_B -CLASS_MEMBERS/;

INSTALLATION
     perl Makefile.PL
     make
     make test
     make install

DESCRIPTION
    Perl class instances are mostly blessed HASHes or GLOBs and store member
    variables either as "$self->{membername}" or "${*$self}{membername}"
    respectively.

    This is very error prone when you start to develope derived classes
    based on such modules. The developer of the derived class must watch the
    member variables of the base class to avoid name conflicts.

    To avoid that "Class::Member::XXX" stores member variables in its own
    namespace prepending the package name to the variable name, e.g.

     package My::New::Module;

     use Class::Member::HASH qw/member_A memberB/;

    will store "member_A" as "$self->{'My::New::Module::member_A'}".

    To make access to these members easier it exports access functions into
    the callers namespace. To access "member_A" you simply call.

     $self->member_A;               # read access
     $self->member_A($new_value);   # write access
     $self->member_A=$new_value;    # write access (used as lvalue)

    "Class::Member::HASH" and "Class::Member::GLOB" are used if your objects
    are HASH or GLOB references. But sometimes you do not know whether your
    instances are GLOBs or HASHes (Consider developement of derived classes
    where the base class is likely to be changed.). In this case use
    "Class::Member" and the methods are defined at compile time to handle
    each type of objects, GLOBs and HASHes. But the first access to a method
    redefines it according to the actual object type. Thus, the first access
    will last slightly longer but all subsequent calls are executed at the
    same speed as "Class::Member::GLOB" or "Class::Member::HASH".

    "Class::Member::Dynamic" is used if your objects can be GLOBs and HASHes
    at the same time. The actual type is determined at each access and the
    appropriate action is taken.

    In addition to member names there are a few options that can be given:
    "-CLASS_MEMBERS". It lets the "import()" function create an array named
    @CLASS_MEMBERS in the caller's namespace that contains the names of all
    methods it defines. Thus, you can create a contructor that expects named
    parameters where each name corresponds to a class member:

     use Class::Member qw/member_A member_B -CLASS_MEMBERS/;
     our @CLASS_MEMBERS;
     
 sub new {
       my $parent=shift;
       my $class=ref($parent) || $parent;
       my $I=bless {}=>$class;
       my %o=@_;
     
   if( ref($parent) ) {         # inherit first
         foreach my $m (@CLASS_MEMBERS) {
           $I->$m=$parent->$m;
         }
       }
     
   # then override with named parameters
       foreach my $m (@CLASS_MEMBERS) {
         $I->$m=$o{$m} if( exists $o{$m} );
       }
     
   $I->init;
     
   return $I;
     }

    Further, if you use one of "Class::Member::HASH" or
    "Class::Member::GLOB" a constructor method can be created automatically.
    Just add "-NEW" or "-NEW=name" to the "use()" call. The first form
    creates a "new()" method that is implemented as shown except of the
    "$I->init" call. The 2nd form can be used if your constructor must not
    be named "new".

    What happens if one "Class::Member" based class inherits the constructor
    from another "Class::Member" based class? In this case the inherited
    contructor works for the @CLASS_MEMBERS of the base class as well as the
    derived class. For example:

     package Base;
     use Class::Member::HASH qw/-NEW -CLASS_MEMBERS el1 el2/;

     package Inherited;
     use Class::Member::HASH qw/-CLASS_MEMBERS el3/;
     use base qw/Base/;

    Now "Inherited-"new> calls the constructor of the base class but one can
    pass "el1", "el2" as well as "el3" parameters.

    The "$I->init" call is added by specifying the "-INIT" or "-INIT=name"
    option. If given a new function "&{I N I T}" is created in the caller's
    namespace to hold the name of the "init()" method. Yes, the symbol name
    does contain spaces to make it harder to change by chance. You don't
    normally have to care about it. Again, the "-INIT=name" form is used if
    your "init()" method is not named "init".

    The "init()" method itself is provided by you.

    More detailed here is how the initializer is called:

     my $init=$self->can('I N I T');
     if( $init ) {
       $init=$init->();
       $self->$init;
     }

    That means the constructor looks if the class itself or one of the base
    classes provides a "I N I T" method (the name includes spaces between
    each pair of characters). If so it calls that method to fetch the
    initializer name. The last step calls the initializer itself.

AUTHOR
    Torsten Foertsch <Torsten.Foertsch@gmx.net>

SEE ALSO
    Class::Member::HASH, Class::Member::GLOB, Class::Member::Dynamic

COPYRIGHT
    Copyright 2003-2008 Torsten Foertsch.

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.