NAME

Class::Accessor::Ref - Access members by reference

SYNOPSIS

package Foo;
use base qw(Class::Accessor::Ref);
use Some::API;

my @members = qw(fruit color);
Foo->mk_accessors(@members);     # as with Class::Accessor
Foo->mk_refaccessors(@members);

my $obj = Foo->new({fruit => 'grape', color => 'green'});
Some::API::redden($obj->_ref_color);        # OR
Some::API::redden($obj->get_ref('color'));
print $obj->color;               # prints 'red'

# safe against typos in memeber name
${ $obj->get_ref('color') } =~ s/^(.)/\U$1/;

DESCRIPTION

This is an extension of Class::Accessor that allows taking a reference of members of an object. This is typically useful when your class implementation uses a third-party module that expects an in/out parameter in its interface.

Without Class::Accessor::Ref, you might try to do somethin like

my $reference = \$obj->member;   # WRONG!
Some::API::call($reference);

But that takes a reference to a copy of $obj->member, and is thus not useful if you want to use the reference to later change the member's value.

It is quite possible to do something like

my $reference = \$obj->{member}; # right, but risky

But then you will get no errors if you accidentally mistype the member's name.

Class::Accessor::Ref is used very similarly to Class::Accessor -- just subclass it instead of Class::Accessor in your module, and call mk_accessors on the fields you want to generate accessors for. Then, call mk_refaccessors on the subset of the fields you want reference-taking accessors generated for. The accessors will be automatically named _ref_FIELD. You can continue to use the normal (non-reference) accessors as before whenever appropriate.

Methods

mk_refaccessor

Class->mk_refaccessors(@fields);

This creates accessor methods for each named field given in @fields. Foreach field in @fields it will generate one accessor called "_ref_field()". Normal accessors for the fields *must* have already been created with Class::Accessor::mk_accessors(). For example:

# Generates _ref_foo(), _ref_bar() but not _ref_baz():
#     Class->mk_accessors(qw(foo bar baz));
#     Class->mk_refaccessors(qw(foo bar));

It is up to the user of this reference to know what to do with it.

get_ref

$obj->get_ref(@field_names)

This returns references to members of $obj, specified by name in @field_names. In scalar context, returns a reference to the first field. This method is useful if you want to fetch several references from the object at once, or if you don't like the _ref_ prefix.

# Get referece to $obj->{foo}
#     $fooref = $obj->get_ref('foo');
#
# Get several references at once
#     ($fooref, $barref) = $obj->get_ref(qw/foo bar/);
#
# Stringify the reference, not the number "1":
#     print "\$obj->{foo} is at " . $obj->get_ref('foo');

CAVEATS

Class::Accessor::Ref generates methods called _ref_SOMETHING in the caller's namespace. Having an existing member whose name begins with _ref_ would render the normal accessor to that member inaccessible, so don't do that.

One point of Class::Accessor is to allow you to avoid changing members directly. Since whoever gets hold of the return value of a _ref_ accessor can circumvent any validations you may have imposed on the member (for example, by overriding the normal setter method), this can be considered somewhat unsafe. The main use of Class::Accessor::Ref is inside class implementations, where you have control over who you trust with giving a reference to your private data and who you don't.

AUTHOR

Gaal Yahas <gaal@forum2.org>

SEE ALSO

Class::Accessor