Class::Mix - dynamic class mixing
use Class::Mix qw(mix_class);
$foobar_object = mix_class("Foo", "Bar")->new;
$digest_class = mix_class("Foo", "Bar", {prefix=>"Digest::"});
use Class::Mix qw(genpkg);
$package = genpkg;
$package = genpkg("Digest::Foo::");
The "mix_class" function provided by this module dynamically generates
`anonymous' classes with specified inheritance.
- mix_class(ITEMS ...)
- This function is used to dynamically generate `anonymous'
classes by mixing pre-existing classes. This is useful where an incomplete
class requires use of a mixin in order to become instantiable, several
suitable mixins are available, and it is desired to make the choice
between mixins at runtime.
Each ITEM in the argument list is either the name of a class to
inherit from (a parent class) or a reference to a hash of options. The
@ISA list of the mixture class is set to the list of parent class names,
in the order supplied. The options that may be supplied are:
- mro
- Specifies the desired method resolution order (MRO) of the
mixture class. See mro for details of the valid values and the default
determined by Perl. Typically, this should be set to c3 if mixing
into an existing C3-based class hierarchy.
- prefix
- Specifies where the resulting package will go. May be
"undef" to indicate that the caller doesn't care (which is the
default state). Otherwise it must be either the empty string (to create a
top-level package) or a bareword followed by "::" (to create a
package under that name). For example, "Digest::" could be
specified to ensure that the resulting package has a name starting with
"Digest::", so that "Digest->new" will accept it as
the name of a message digest algorithm.
The function generates a class of the form described by the arguments, and
returns its name. The same class will be returned by repeated invocations with
the same parent class list and options. The returned name may be used to call
a constructor or other class methods of the mixed class.
A class name must be returned because there is no such thing as an anonymous
class in Perl. Classes are referenced by name. The names that are generated by
this function are unique and insignificant. See "genpkg" below for
more information.
If fewer than two classes to inherit from are specified, the function tries to
avoid generating a separate class for the mixture. If only one parent class is
specified then that class may be returned, and if no parent classes are
specified then "UNIVERSAL" may be returned. This provides the
desired inheritance without creating superfluous classes. These special cases
only apply if the options are compatible with the pre-existing class.
This function relies on the classes it returns remaining unmodified in order to
be returned by future invocations. If you want to modify your
dynamically-generated `anonymous' classes, use "genpkg"
(below).
- genpkg([PREFIX])
- This function selects and returns a package name that has
not been previously used. The name returned is an ordinary bareword-form
package name, and can be used as the second argument to "bless"
and in all other ways that package names are used. The package is
initially empty.
The package names returned by this function are of a type that should not be
used as ordinary fixed module names. However, it is not possible to
entirely prevent a clash. This function checks that the package name it is
about to return has not already been used, and will avoid returning such
names, but it cannot guarantee that a later-loaded module will not create
a clash.
PREFIX, if present, specifies where the resulting package will go. It must
be either the empty string (to create a top-level package) or a bareword
followed by "::" (to create a package under that name). For
example, "Digest::" could be specified to ensure that the
resulting package has a name starting with "Digest::", so that
"Digest->new" will accept it as the name of a message digest
algorithm. If the PREFIX is not supplied, the caller is not expressing any
preference.
Class::Generate, mro
Andrew Main (Zefram) <
[email protected]>
Copyright (C) 2004, 2006, 2009, 2010, 2011, 2017 Andrew Main (Zefram)
<
[email protected]>
This module is free software; you can redistribute it and/or modify it under the
same terms as Perl itself.