Class::Method::Modifiers - phpMan

NAME
    Class::Method::Modifiers - Provides Moose-like method modifiers

VERSION
    version 2.13

SYNOPSIS
        package Child;
        use parent 'MyParent';
        use Class::Method::Modifiers;

        sub new_method { }

        before 'old_method' => sub {
            carp "old_method is deprecated, use new_method";
        };

        around 'other_method' => sub {
            my $orig = shift;
            my $ret = $orig->(@_);
            return $ret =~ /\d/ ? $ret : lc $ret;
        };

        after 'private', 'protected' => sub {
            debug "finished calling a dangerous method";
        };

        use Class::Method::Modifiers qw(fresh);

        fresh 'not_in_hierarchy' => sub {
            warn "freshly added method\n";
        };

DESCRIPTION
    Method modifiers are a convenient feature from the CLOS (Common Lisp
    Object System) world.

    In its most basic form, a method modifier is just a method that calls
    "$self->SUPER::foo(@_)". I for one have trouble remembering that exact
    invocation, so my classes seldom re-dispatch to their base classes. Very
    bad!

    "Class::Method::Modifiers" provides three modifiers: "before", "around",
    and "after". "before" and "after" are run just before and after the
    method they modify, but can not really affect that original method.
    "around" is run in place of the original method, with a hook to easily
    call that original method. See the "MODIFIERS" section for more details
    on how the particular modifiers work.

    One clear benefit of using "Class::Method::Modifiers" is that you can
    define multiple modifiers in a single namespace. These separate
    modifiers don't need to know about each other. This makes top-down
    design easy. Have a base class that provides the skeleton methods of
    each operation, and have plugins modify those methods to flesh out the
    specifics.

    Parent classes need not know about "Class::Method::Modifiers". This
    means you should be able to modify methods in *any* subclass. See
    Term::VT102::ZeroBased for an example of subclassing with
    "Class::Method::Modifiers".

    In short, "Class::Method::Modifiers" solves the problem of making sure
    you call "$self->SUPER::foo(@_)", and provides a cleaner interface for
    it.

    As of version 1.00, "Class::Method::Modifiers" is faster in some cases
    than Moose. See benchmark/method_modifiers.pl in the Moose distribution.

    "Class::Method::Modifiers" also provides an additional "modifier" type,
    "fresh"; see below.

MODIFIERS
    All modifiers let you modify one or multiple methods at a time. The
    names of multiple methods can be provided as a list or as an
    array-reference. Examples:

     before 'method' => sub { ... };
     before 'method1', 'method2' => sub { ... };
     before [ 'method1', 'method2' ] => sub { ... };

  before method(s) => sub { ... };
    "before" is called before the method it is modifying. Its return value
    is totally ignored. It receives the same @_ as the method it is
    modifying would have received. You can modify the @_ the original method
    will receive by changing $_[0] and friends (or by changing anything
    inside a reference). This is a feature!

  after method(s) => sub { ... };
    "after" is called after the method it is modifying. Its return value is
    totally ignored. It receives the same @_ as the method it is modifying
    received, mostly. The original method can modify @_ (such as by changing
    $_[0] or references) and "after" will see the modified version. If you
    don't like this behavior, specify both a "before" and "after", and copy
    the @_ during "before" for "after" to use.

  around method(s) => sub { ... };
    "around" is called instead of the method it is modifying. The method
    you're overriding is passed in as the first argument (called $orig by
    convention). Watch out for contextual return values of $orig.

    You can use "around" to:

    Pass $orig a different @_
            around 'method' => sub {
                my $orig = shift;
                my $self = shift;
                $orig->($self, reverse @_);
            };

    Munge the return value of $orig
            around 'method' => sub {
                my $orig = shift;
                ucfirst $orig->(@_);
            };

    Avoid calling $orig -- conditionally
            around 'method' => sub {
                my $orig = shift;
                return $orig->(@_) if time() % 2;
                return "no dice, captain";
            };

  fresh method(s) => sub { ... };
    (Available since version 2.00)

    Unlike the other modifiers, this does not modify an existing method.
    Ordinarily, "fresh" merely installs the coderef as a method in the
    appropriate class; but if the class hierarchy already contains a method
    of the same name, an exception is thrown. The idea of this "modifier" is
    to increase safety when subclassing. Suppose you're writing a subclass
    of a class Some::Base, and adding a new method:

        package My::Subclass;
        use base 'Some::Base';

        sub foo { ... }

    If a later version of Some::Base also adds a new method named "foo",
    your method will shadow that method. Alternatively, you can use "fresh"
    to install the additional method into your subclass:

        package My::Subclass;
        use base 'Some::Base';

        use Class::Method::Modifiers 'fresh';

        fresh 'foo' => sub { ... };

    Now upgrading Some::Base to a version with a conflicting "foo" method
    will cause an exception to be thrown; seeing that error will give you
    the opportunity to fix the problem (perhaps by picking a different
    method name in your subclass, or similar).

    Creating fresh methods with "install_modifier" (see below) provides a
    way to get similar safety benefits when adding local monkeypatches to
    existing classes; see
    <http://aaroncrane.co.uk/talks/monkey_patching_subclassing/>.

    For API compatibility reasons, this function is exported only when you
    ask for it specifically, or for ":all".

  install_modifier $package, $type, @names, sub { ... }
    "install_modifier" is like "before", "after", "around", and "fresh" but
    it also lets you dynamically select the modifier type ('before',
    'after', 'around', 'fresh') and package that the method modifiers are
    installed into. This expert-level function is exported only when you ask
    for it specifically, or for ":all".

NOTES
    All three normal modifiers; "before", "after", and "around"; are
    exported into your namespace by default. You may "use
    Class::Method::Modifiers ()" to avoid modifying your namespace. I may
    steal more features from Moose, namely "super", "override", "inner",
    "augment", and whatever the Moose folks come up with next.

    Note that the syntax and semantics for these modifiers is directly
    borrowed from Moose (the implementations, however, are not).

    Class::Trigger shares a few similarities with
    "Class::Method::Modifiers", and they even have some overlap in purpose
    -- both can be used to implement highly pluggable applications. The
    difference is that Class::Trigger provides a mechanism for easily
    letting parent classes to invoke hooks defined by other code.
    "Class::Method::Modifiers" provides a way of overriding/augmenting
    methods safely, and the parent class need not know about it.

  :lvalue METHODS
    When adding "before" or "after" modifiers, the wrapper method will be an
    lvalue method if the wrapped sub is, and assigning to the method will
    propagate to the wrapped method as expected. For "around" modifiers, it
    is the modifier sub that determines if the wrapper method is an lvalue
    method.

CAVEATS
    It is erroneous to modify a method that doesn't exist in your class's
    inheritance hierarchy. If this occurs, an exception will be thrown when
    the modifier is defined.

    It doesn't yet play well with "caller". There are some "TODO" tests for
    this. Don't get your hopes up though!

    Applying modifiers to array lvalue methods is not fully supported.
    Attempting to assign to an array lvalue method that has an "after"
    modifier applied will result in an error. Array lvalue methods are not
    well supported by perl in general, and should be avoided.

MAJOR VERSION CHANGES
    This module was bumped to 1.00 following a complete reimplementation, to
    indicate breaking backwards compatibility. The "guard" modifier was
    removed, and the internals are completely different.

    The new version is a few times faster with half the code. It's now even
    faster than Moose.

    Any code that just used modifiers should not change in behavior, except
    to become more correct. And, of course, faster. :)

SEE ALSO
    *   Class::Method::Modifiers::Fast

    *   Moose

    *   Class::Trigger

    *   Class::MOP::Method::Wrapped

    *   MRO::Compat

    *   CLOS <https://en.wikipedia.org/wiki/Common_Lisp_Object_System>

ACKNOWLEDGEMENTS
    Thanks to Stevan Little for Moose, I would never have known about method
    modifiers otherwise.

    Thanks to Matt Trout and Stevan Little for their advice.

SUPPORT
    Bugs may be submitted through the RT bug tracker
    <https://rt.cpan.org/Public/Dist/Display.html?Name=Class-Method-Modifier
    s> (or bug-Class-Method-Modifiers AT rt.org
    <mailto:bug-Class-Method-Modifiers AT rt.org>).

AUTHOR
    Shawn M Moore <sartak AT gmail.com>

CONTRIBUTORS
    *   Karen Etheridge <ether AT cpan.org>

    *   Shawn M Moore <code AT sartak.org>

    *   Graham Knop <haarg AT haarg.org>

    *   Aaron Crane <arc AT cpan.org>

    *   Peter Rabbitson <ribasushi AT cpan.org>

    *   Justin Hunter <justin.d.hunter AT gmail.com>

    *   David Steinbrunner <dsteinbrunner AT pobox.com>

    *   gfx <gfuji AT cpan.org>

    *   mannih <github AT lxxi.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2007 by Shawn M Moore.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.