Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
MakeMethods::Template:UservContributed PerlMakeMethods::Template::Universal(3)

NAME
       Class::MakeMethods::Template::Universal - Meta-methods for any type of
       object

SYNOPSIS
	 package MyObject;
	 use Class::MakeMethods::Template::Universal (
	   'no_op' => [	'twiddle' ],
	   'croak' => [	'fail',	{ croak_msg => 'Curses!' } ]
	 );

	 package main;

	 MyObject->twiddle;		       # Does nothing
	 if ( $foiled )	{ MyObject->fail() }   # Dies with croak_msg

DESCRIPTION
UNIVERSAL META-METHODS
       The following meta-methods and behaviors	are applicable across multiple
       types of	classes	and objects.

   Universal:generic
       This is not a directly-invokable	method type, but instead provides code
       expressions for use in other method-generators.

       You can use any of these	features in your meta-method interfaces
       without explicitly importing them.

       Modifiers

       o   --private

	   Causes the method to	croak if it is called from outside of the
	   package which originally declared it.

	   Note	that this protection can currently be circumvented if your
	   class provides the method_init behavior, or another subroutine that
	   calls methods by name.

       o   --protected

	   Causes the method to	croak if it is called from a package other
	   than	the declaring package and its inheritors.

	   Note	that this protection can currently be circumvented if your
	   class provides the method_init behavior, or another subroutine that
	   calls methods by name.

       o   --public

	   Cancels any previous	-private or -protected declaration.

       o   --self_closure

	   Causes the method to	return a function reference which is bound to
	   the arguments provided when it is first called.

	   For examples	of usage, see the test scripts in t/*closure.t.

       o   --lvalue

	   Adds	the ":lvalue" attribute	to the subroutine declaration.

	   For examples	of usage, see the test scripts in t/*lvalue.t.

       o   --warn_calls

	   For diagnostic purposes, call warn with the object reference,
	   method name,	and arguments before executing the body	of the method.

       Behaviors

       o   attributes

	   Runtime access to method parameters.

       o   no_op -- See	below.

       o   croak -- See	below.

       o   method_init -- See below.

   no_op
       For each	meta-method, creates a method with an empty body.

	 use Class::MakeMethods::Template::Universal (
	   'no_op' => [	'foo bar baz' ],
	 );

       You might want to create	and use	such methods to	provide	hooks for
       subclass	activity.

       No interfaces or	parameters supported.

   croak
       For each	meta-method, creates a method which will croak if called.

	 use Class::MakeMethods::Template::Universal (
	   'croak' => [	'foo bar baz' ],
	 );

       This is intended	to support the use of abstract methods,	that must be
       overidden in a useful subclass.

       If each subclass	is expected to provide an implementation of a given
       method, using this abstract method will replace the generic error
       message below with the clearer, more explicit error message that
       follows it:

	 Can't locate object method "foo" via package "My::Subclass"
	 The "foo" method is abstract and can not be called on My::Subclass

       However,	note that the existence	of this	method will be detected	by
       UNIVERSAL::can(), so it is not suitable for use in optional interfaces,
       for which you may wish to be able to detect whether the method is
       supported or not.

       The -unsupported	and -prohibited	interfaces provide alternate error
       messages, or a custom error message can be provided using the
       'croak_msg' parameter.

   method_init
       Creates a method	that accepts a hash of key-value pairs,	or a reference
       to hash of such pairs. For each pair, the key is	interpreted as the
       name of a method	to call, and the value is the argument to be passed to
       that method.

       Sample declaration and usage:

	 package MyObject;
	 use Class::MakeMethods::Template::Universal (
	   method_init => 'init',
	 );
	 ...

	 my $object = MyObject->new()
	 $object->init(	foo => 'Foozle', bar =>	'Barbados' );

	 # Equivalent to:
	 $object->foo('Foozle');
	 $object->bar('Barbados');

       You might want to create	and use	such methods to	allow easy
       initialization of multiple object or class parameters in	a single call.

       Note: including methods of this type will circumvent the	protection of
       "private" and "protected" methods, because it an	outside	caller can
       cause an	object to call specific	methods	on itself, bypassing the
       privacy protection.

   forward_methods
       Creates a method	which delegates	to an object provided by another
       method.

       Example:

	 use Class::MakeMethods::Template::Universal
	   forward_methods => [
		--target=> 'whistle', w,
	       [ 'x', 'y' ], { target=>	'xylophone' },
	       { name=>'z', target=>'zither', target_args=>[123], method_name=>do_zed },
	     ];

       Example:	The above defines that method "w" will be handled by the
       calling "w" on the object returned by "whistle",	whilst methods "x" and
       "y" will	be handled by "xylophone", and method "z" will be handled by
       calling "do_zed"	on the object returned by calling "zither(123)".

       Interfaces:

       forward (default)
	   Calls the method on the target object. If the target	object is
	   missing, croaks at runtime with a message saying "Can't forward bar
	   because bar is empty."

       delegate
	   Calls the method on the target object, if present. If the target
	   object is missing, returns nothing.

       Parameters: The following additional parameters are supported:

       target
	   Required. The name of the method that will provide the object that
	   will	handle the operation.

       target_args
	   Optional ref	to an array of arguments to be passed to the target
	   method.

       method_name
	   The name of the method to call on the handling object. Defaults to
	   the name of the meta-method being created.

SEE ALSO
       See Class::MakeMethods for general information about this distribution.

       See Class::MakeMethods::Template	for information	about this family of
       subclasses.

perl v5.24.1			  2004-09-0MakeMethods::Template::Universal(3)

NAME | SYNOPSIS | DESCRIPTION | UNIVERSAL META-METHODS | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=Class::MakeMethods::Template::Universal&sektion=3&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help