MakeMethods(3) User Contributed Perl Documentation MakeMethods(3)NAMEClass::MakeMethods - Generate common types of methods
SYNOPSIS
# Generates methods for your object when you "use" it.
package MyObject;
use Class::MakeMethods::Standard::Hash (
'new' => 'new',
'scalar' => 'foo',
'scalar' => 'bar',
);
# The generated methods can be called just like normal ones
my $obj = MyObject->new( foo => "Foozle", bar => "Bozzle" );
print $obj->foo();
$obj->bar("Barbados");
DESCRIPTION
The Class::MakeMethods framework allows Perl class developers to
quickly define common types of methods. When a module "use"s
Class::MakeMethods or one of its subclasses, it can select from a
variety of supported method types, and specify a name for each method
desired. The methods are dynamically generated and installed in the
calling package.
Construction of the individual methods is handled by subclasses. This
delegation approach allows for a wide variety of method-generation
techniques to be supported, each by a different subclass. Subclasses
can also be added to provide support for new types of methods.
Over a dozen subclasses are available, including implementations of a
variety of different method-generation techniques. Each subclass
generates several types of methods, with some supporting their own
open-eneded extension syntax, for hundreds of possible combinations of
method types.
GETTING STARTED
Motivation
"Make easy things easier."
This module addresses a problem encountered in object-oriented
development wherein numerous methods are defined which differ only
slightly from each other.
A common example is accessor methods for hash-based object attributes,
which allow you to get and set the value $self->{'foo'} by calling a
method $self->foo().
These methods are generally quite simple, requiring only a couple of
lines of Perl, but in sufficient bulk, they can cut down on the
maintainability of large classes.
Class::MakeMethods allows you to simply declare those methods to be of
a predefined type, and it generates and installs the necessary methods
in your package at compile-time.
A Contrived Example
Object-oriented Perl code is widespread -- you've probably seen code
like the below a million times:
my $obj = MyStruct->new( foo=>"Foozle", bar=>"Bozzle" );
if ( $obj->foo() =~ /foo/i ) {
$obj->bar("Barbados!");
}
print $obj->summary();
(If this doesn't look familiar, take a moment to read perlboot and
you'll soon learn more than's good for you.)
Typically, this involves creating numerous subroutines that follow a
handful of common patterns, like constructor methods and accessor
methods. The classic example is accessor methods for hash-based object
attributes, which allow you to get and set the value self->{foo} by
calling a method self->foo(). These methods are generally quite
simple, requiring only a couple of lines of Perl, but in sufficient
bulk, they can cut down on the maintainability of large classes.
Here's a possible implementation for the class whose interface is shown
above:
package MyStruct;
sub new {
my $callee = shift;
my $self = bless { @_ }, (ref $callee || $callee);
return $self;
}
sub foo {
my $self = shift;
if ( scalar @_ ) {
$self->{'foo'} = shift();
} else {
$self->{'foo'}
}
}
sub bar {
my $self = shift;
if ( scalar @_ ) {
$self->{'bar'} = shift();
} else {
$self->{'bar'}
}
}
sub summary {
my $self = shift;
join(', ', map { "\u$_: " . $self->$_() } qw( foo bar ) )
}
Note in particular that the foo and bar methods are almost identical,
and that the new method could be used for almost any class; this is
precisely the type of redundancy Class::MakeMethods addresses.
Class::MakeMethods allows you to simply declare those methods to be of
a predefined type, and it generates and installs the necessary methods
in your package at compile-time.
Here's the equivalent declaration for that same basic class:
package MyStruct;
use Class::MakeMethods::Standard::Hash (
'new' => 'new',
'scalar' => 'foo',
'scalar' => 'bar',
);
sub summary {
my $self = shift;
join(', ', map { "\u$_: " . $self->$_() } qw( foo bar ) )
}
This is the basic purpose of Class::MakeMethods: The "boring" pieces of
code have been replaced by succinct declarations, placing the focus on
the "unique" or "custom" pieces.
Finding the Method Types You Need
Once you've grasped the basic idea -- simplifying repetitive code by
generating and installing methods on demand -- the remaining complexity
basically boils down to figuring out which arguments to pass to
generate the specific methods you want.
Unfortunately, this is not a trivial task, as there are dozens of
different types of methods that can be generated, each with a variety
of options, and several alternative ways to write each method
declaration. You may prefer to start by just finding a few examples
that you can modify to accomplish your immediate needs, and defer
investigating all of the extras until you're ready to take a closer
look.
Other Documentation
The remainder of this document focuses on points of usage that are
common across all subclasses, and describes how to create your own
subclasses.
If this is your first exposure to Class::MakeMethods, you may want to
skim over the rest of this document, then take a look at the examples
and one or two of the method-generating subclasses to get a more
concrete sense of typical usage, before returning to the details
presented below.
· A collection of sample uses is available in
Class::MakeMethods::Docs::Examples.
· Some of the most common object and class methods are available from
Class::MakeMethods::Standard::Hash,
Class::MakeMethods::Standard::Global and
Class::MakeMethods::Standard::Universal.
· If you need a bit more flexibility, see
Class::MakeMethods::Composite for method generators which offer
more customization options, including pre- and post-method callback
hooks.
· For the largest collection of methods and options, see
Class::MakeMethods::Template, which uses a system of dynamic code
generation to allow endless variation.
· A listing of available method types from each of the different
subclasses is provided in Class::MakeMethods::Docs::Catalog.
CLASS ARCHITECTURE
Because there are so many common types of methods one might wish to
generate, the Class::MakeMethods framework provides an extensible
system based on subclasses.
When your code requests a method, the MakeMethods base class performs
some standard argument parsing, delegates the construction of the
actual method to the appropriate subclass, and then installs whatever
method the subclass returns.
The MakeMethods Base Class
The Class::MakeMethods package defines a superclass for method-
generating modules, and provides a calling convention, on-the-fly
subclass loading, and subroutine installation that will be shared by
all subclasses.
The superclass also lets you generate several different types of
methods in a single call, and will automatically load named subclasses
the first time they're used.
The Method Generator Subclasses
The type of method that gets created is controlled by the specific
subclass and generator function you request. For example,
"Class::MakeMethods::Standard::Hash" has a generator function
"scalar()", which is responsible for generating simple scalar-accessor
methods for blessed-hash objects.
Each generator function specified is passed the arguments specifying
the method the caller wants, and produces a closure or eval-able
sequence of Perl statements representing the ready-to-install function.
Included Subclasses
Because each subclass defines its own set of method types and
customization options, a key step is to find your way to the
appropriate subclasses.
Standard (See Class::MakeMethods::Standard.)
Generally you will want to begin with the Standard::Hash subclass,
to create constructor and accessor methods for working with
blessed-hash objects (or you might choose the Standard::Array
subclass instead). The Standard::Global subclass provides methods
for class data shared by all objects in a class.
Each Standard method declaration can optionally include a hash of
associated parameters, which allows you to tweak some of the
characteristics of the methods. Subroutines are bound as closures
to a hash of each method's name and parameters. Standard::Hash and
Standard::Array provide object constructor and accessors. The
Standard::Global provides for static data shared by all instances
and subclasses, while the data for Standard::Inheritable methods
trace the inheritance tree to find values, and can be overriden for
any subclass or instance.
Composite (See Class::MakeMethods::Composite.)
For additional customization options, check out the Composite
subclasses, which allow you to select from a more varied set of
implementations and which allow you to adjust any specific method
by adding your own code-refs to be run before or after it.
Subroutines are bound as closures to a hash of each method's name
and optional additional data, and to one or more subroutine
references which make up the composite behavior of the method.
Composite::Hash and Composite::Array provide object constructor and
accessors. The Composite::Global provides for static data shared by
all instances and subclasses, while the data for
Composite::Inheritable methods can be overriden for any subclass or
instance.
Template (See Class::MakeMethods::Template.)
The Template subclasses provide an open-ended structure for objects
that assemble Perl code on the fly into cachable closure-generating
subroutines; if the method you need isn't included, you can extend
existing methods by re-defining just the snippet of code that's
different.
Class::MakeMethods::Template extends MakeMethods with a text
templating system that can assemble Perl code fragments into a
desired subroutine. The code for generated methods is eval'd once
for each type, and then repeatedly bound as closures to method-
specific data for better performance.
Templates for dozens of types of constructor, accessor, and mutator
methods are included, ranging from from the mundane (constructors
and value accessors for hash and array slots) to the esoteric
(inheritable class data and "inside-out" accessors with external
indexes).
Basic (See Class::MakeMethods::Basic.)
The Basic subclasses provide stripped down method generators with
no configurable options, for minimal functionality (and minimum
overhead).
Subroutines are bound as closures to the name of each method.
Basic::Hash and Basic::Array provide simple object constructors and
accessors. Basic::Global provides basic global-data accessors.
Emulators (See Class::MakeMethods::Emulator.)
In several cases, Class::MakeMethods provides functionality closely
equivalent to that of an existing module, and it is simple to map
the existing module's interface to that of Class::MakeMethods.
Emulators are included for Class::MethodMaker,
Class::Accessor::Fast, Class::Data::Inheritable, Class::Singleton,
and Class::Struct, each of which passes the original module's test
suite, usually requiring only that the name of the module be
changed.
Extending
Class::MakeMethods can be extended by creating subclasses that
define additional method-generation functions. Callers can then
specify the name of your subclass and generator function in their
"use Call::MakeMethods ..." statements and your function will be
invoked to produce the required closures. See "EXTENDING" for more
information.
Naming Convention for Generated Method Types
Method generation functions in this document are often referred to
using the 'MakerClass:MethodType' or
'MakerGroup::MakerSubclass:MethodType' naming conventions. As you will
see, these are simply the names of Perl packages and the names of
functions that are contained in those packages.
The included subclasses are grouped into several major groups, so the
names used by the included subclasses and method types reflect three
axes of variation, "Group::Subclass:Type":
Maker Group
Each group shares a similar style of technical implementation and
level of complexity. For example, the "Standard::*" packages are
all simple, while the "Composite::*" packages all support pre- and
post-conditions.
(For a listing of the four main groups of included subclasses, see
"Included Subclasses"" in ".)
Maker Subclass
Each subclass generates methods for a similar level of scoping or
underlying object type. For example, the *::Hash packages all make
methods for objects based on blessed hashes, while the *::Global
packages make methods that access class-wide data that will be
shared between all objects in a class.
Method Type
Each method type produces a similar type of constructor or
accessor. For examples, the *:new methods are all constructors,
while the "::scalar" methods are all accessors that allow you to
get and set a single scalar value.
Bearing that in mind, you should be able to guess the intent of many of
the method types based on their names alone; when you see
"Standard::Hash:scalar" you can read it as "a type of method to access
a scalar value stored in a hash-based object, with a standard
implementation style" and know that it's going to call the scalar()
function in the Class::MakeMethods::Standard::Hash package to generate
the requested method.
USAGE
The supported method types, and the kinds of arguments they expect,
vary from subclass to subclass; see the documentation of each subclass
for details.
However, the features described below are applicable to all subclasses.
Invocation
Methods are dynamically generated and installed into the calling
package when you "use Class::MakeMethods (...)" or one of its
subclasses, or if you later call "Class::MakeMethods->make(...)".
The arguments to "use" or "make" should be pairs of a generator type
name and an associated array of method-name arguments to pass to the
generator.
· use Class::MakeMethods::MakerClass (
'MethodType' => [ Arguments ], ...
);
· Class::MakeMethods::MakerClass->make (
'MethodType' => [ Arguments ], ...
);
You may select a specific subclass of Class::MakeMethods for a single
generator-type/argument pair by prefixing the type name with a subclass
name and a colon.
· use Class::MakeMethods (
'MakerClass:MethodType' => [ Arguments ], ...
);
· Class::MakeMethods->make (
'MakerClass:MethodType' => [ Arguments ], ...
);
The difference between "use" and "make" is primarily one of precedence;
the "use" keyword acts as a BEGIN block, and is thus evaluated before
"make" would be. (See "About Precedence" for additional discussion of
this issue.)
Alternative Invocation
If you want methods to be declared at run-time when a previously-
unknown method is invoked, see Class::MakeMethods::Autoload.
· use Class::MakeMethods::Autoload 'MakerClass:MethodType';
If you are using Perl version 5.6 or later, see
Class::MakeMethods::Attribute for an additional declaration syntax for
generated methods.
· use Class::MakeMethods::Attribute 'MakerClass';
sub name :MakeMethod('MethodType' => Arguments);
About Precedence
Rather than passing the method declaration arguments when you "use" one
of these packages, you may instead pass them to a subsequent call to
the class method "make".
The difference between "use" and "make" is primarily one of precedence;
the "use" keyword acts as a BEGIN block, and is thus evaluated before
"make" would be. In particular, a "use" at the top of a file will be
executed before any subroutine declarations later in the file have been
seen, whereas a "make" at the same point in the file will not.
By default, Class::MakeMethods will not install generated methods over
any pre-existing methods in the target class. To override this you can
pass "-ForceInstall => 1" as initial arguments to "use" or "make".
If the same method is declared multiple times, earlier calls to "use"
or "make()" win over later ones, but within each call, later
declarations superceed earlier ones.
Here are some examples of the results of these precedence rules:
# 1 - use, before
use Class::MakeMethods::Standard::Hash (
'scalar'=>['baz'] # baz() not seen yet, so we generate, install
);
sub baz { 1 } # Subsequent declaration overwrites it, with warning
# 2 - use, after
sub foo { 1 }
use Class::MakeMethods::Standard::Hash (
'scalar'=>['foo'] # foo() is already declared, so has no effect
);
# 3 - use, after, Force
sub bar { 1 }
use Class::MakeMethods::Standard::Hash (
-ForceInstall => 1, # Set flag for following methods...
'scalar' => ['bar'] # ... now overwrites pre-existing bar()
);
# 4 - make, before
Class::MakeMethods::Standard::Hash->make(
'scalar'=>['blip'] # blip() is already declared, so has no effect
);
sub blip { 1 } # Although lower than make(), this "happens" first
# 5 - make, after, Force
sub ping { 1 }
Class::MakeMethods::Standard::Hash->make(
-ForceInstall => 1, # Set flag for following methods...
'scalar' => ['ping'] # ... now overwrites pre-existing ping()
);
Global Options
Global options may be specified as an argument pair with a leading
hyphen. (This distinguishes them from type names, which must be valid
Perl subroutine names, and thus will never begin with a hyphen.)
use Class::MakeMethods::MakerClass (
'-Param' => ParamValue,
'MethodType' => [ Arguments ], ...
);
Option settings apply to all subsequent method declarations within a
single "use" or "make" call.
The below options allow you to control generation and installation of
the requested methods. (Some subclasses may support additional options;
see their documentation for details.)
-TargetClass
By default, the methods are installed in the first package in the
caller() stack that is not a Class::MakeMethods subclass; this is
generally the package in which your use or make statement was
issued. To override this you can pass "-TargetClass => package" as
initial arguments to "use" or "make".
This allows you to construct or modify classes "from the outside":
package main;
use Class::MakeMethods::Basic::Hash(
-TargetClass => 'MyWidget',
'new' => ['create'],
'scalar' => ['foo', 'bar'],
);
$o = MyWidget->new( foo => 'Foozle' );
print $o->foo();
-MakerClass
By default, meta-methods are looked up in the package you called
use or make on.
You can override this by passing the "-MakerClass" flag, which
allows you to switch packages for the remainder of the meta-method
types and arguments.
use Class::MakeMethods (
'-MakerClass'=>'MakerClass',
'MethodType' => [ Arguments ]
);
When specifying the MakerClass, you may provide either the trailing
part name of a subclass inside of the "Class::MakeMethods::"
namespace, or a full package name prefixed by "::".
For example, the following four statements are equivalent ways of
declaring a Basic::Hash scalar method named 'foo':
use Class::MakeMethods::Basic::Hash (
'scalar' => [ 'foo' ]
);
use Class::MakeMethods (
'Basic::Hash:scalar' => [ 'foo' ]
);
use Class::MakeMethods (
'-MakerClass'=>'Basic::Hash',
'scalar' => [ 'foo' ]
);
use Class::MakeMethods (
'-MakerClass'=>'::Class::MakeMethods::Basic::Hash',
'scalar' => [ 'foo' ]
);
-ForceInstall
By default, Class::MakeMethods will not install generated methods
over any pre-existing methods in the target class. To override this
you can pass "-ForceInstall => 1" as initial arguments to "use" or
"make".
Note that the "use" keyword acts as a BEGIN block, so a "use" at
the top of a file will be executed before any subroutine
declarations later in the file have been seen. (See "About
Precedence" for additional discussion of this issue.)
Mixing Method Types
A single calling class can combine generated methods from different
MakeMethods subclasses. In general, the only mixing that's problematic
is combinations of methods which depend on different underlying object
types, like using *::Hash and *::Array methods together -- the methods
will be generated, but some of them are guaranteed to fail when
called, depending on whether your object happens to be a blessed
hashref or arrayref.
For example, it's common to mix and match various *::Hash methods, with
a scattering of Global or Inheritable methods:
use Class::MakeMethods (
'Basic::Hash:scalar' => 'foo',
'Composite::Hash:scalar' => [ 'bar' => { post_rules => [] } ],
'Standard::Global:scalar' => 'our_shared_baz'
);
Declaration Syntax
The following types of Simple declarations are supported:
· generator_type => 'method_name'
· generator_type => 'method_1 method_2...'
· generator_type => [ 'method_1', 'method_2', ...]
For a list of the supported values of generator_type, see "STANDARD
CLASSES" in Class::MakeMethods::Docs::Catalog, or the documentation for
each subclass.
For each method name you provide, a subroutine of the indicated type
will be generated and installed under that name in your module.
Method names should start with a letter, followed by zero or more
letters, numbers, or underscores.
Argument Normalization
The following expansion rules are applied to argument pairs to enable
the use of simple strings instead of arrays of arguments.
· Each type can be followed by a single meta-method definition, or by
a reference to an array of them.
· If the argument is provided as a string containing spaces, it is
split and each word is treated as a separate argument.
· It the meta-method type string contains spaces, it is split and
only the first word is used as the type, while the remaining words
are placed at the front of the argument list.
For example, the following statements are equivalent ways of declaring
a pair of Basic::Hash scalar methods named 'foo' and 'bar':
use Class::MakeMethods::Basic::Hash (
'scalar' => [ 'foo', 'bar' ],
);
use Class::MakeMethods::Basic::Hash (
'scalar' => 'foo',
'scalar' => 'bar',
);
use Class::MakeMethods::Basic::Hash (
'scalar' => 'foo bar',
);
use Class::MakeMethods::Basic::Hash (
'scalar foo' => 'bar',
);
(The last of these is clearly a bit peculiar and potentially misleading
if used as shown, but it enables advanced subclasses to provide
convenient formatting for declarations with defaults or modifiers,
such as 'Template::Hash:scalar --private' => 'foo', discussed
elsewhere.)
Parameter Syntax
The Standard syntax also provides several ways to optionally associate
a hash of additional parameters with a given method name.
· generator_type => [
'method_1' => { param=>value... }, ...
]
A hash of parameters to use just for this method name.
(Note: to prevent confusion with self-contained definition hashes,
described below, parameter hashes following a method name must not
contain the key 'name'.)
· generator_type => [
[ 'method_1', 'method_2', ... ] => { param=>value... }
]
Each of these method names gets a copy of the same set of
parameters.
· generator_type => [
{ 'name'=>'method_1', param=>value... }, ...
]
By including the reserved parameter 'name', you create a self-
contained declaration with that name and any associated hash
values.
Simple declarations, as shown in the prior section, are treated as if
they had an empty parameter hash.
Default Parameters
A set of default parameters to be used for several declarations may be
specified using any of the following types of arguments to a method
generator call:
· generator_type => [
'-param' => 'value', 'method_1', 'method_2', ...
]
Set a default value for the specified parameter to be passed to all
subsequent declarations.
· generator_type => [
'--' => { 'param' => 'value', ... }, 'method_1', 'method_2',
...
]
Set default values for one or more parameters to be passed to all
subsequent declarations. Equivalent to a series of '-param' =>
'value' pairs for each pair in the referenced hash.
· generator_type => [
'--special_param', 'method_1', 'method_2', ...
]
Appends to the default value for a special parameter named "--".
This parameter is currently only used by some subclasses; for
details see Class::MakeMethods::Template
Parameters set in these ways are passed to each declaration that
follows it until the end of the method-generator argument array, or
until overridden by another declaration. Parameters specified in a hash
for a specific method name, as discussed above, will override the
defaults of the same name for that particular method.
DIAGNOSTICS
The following warnings and errors may be produced when using
Class::MakeMethods to generate methods. (Note that this list does not
include run-time messages produced by calling the generated methods.)
These messages are classified as follows (listed in increasing order of
desperation):
(Q) A debugging message, only shown if $CONTEXT{Debug} is true
(W) A warning.
(D) A deprecation.
(F) A fatal error in caller's use of the module.
(I) An internal problem with the module or subclasses.
Portions of the message which may vary are denoted with a %s.
Can't interpret meta-method template: argument is empty or undefined
(F)
Can't interpret meta-method template: unknown template name '%s'
(F)
Can't interpret meta-method template: unsupported template type '%s'
(F)
Can't make method %s(): template specifies unknown behavior '%s'
(F)
Can't parse meta-method declaration: argument is empty or undefined
(F) You passed an undefined value or an empty string in the list of
meta-method declarations to use or make.
Can't parse meta-method declaration: missing name attribute.
(F) You included an hash-ref-style meta-method declaration that did
not include the required name attribute. You may have meant this to
be an attributes hash for a previously specified name, but if so we
were unable to locate it.
Can't parse meta-method declaration: unknown template name '%s'
(F) You included a template specifier of the form '-template_name'
in a the list of meta-method declaration, but that template is not
available.
Can't parse meta-method declaration: unsupported declaration type '%s'
(F) You included an unsupported type of value in a list of meta-
method declarations.
Compilation error: %s
(I)
Not an interpretable meta-method: '%s'
(I)
Odd number of arguments passed to %s make
(F) You specified an odd number of arguments in a call to use or
make. The arguments should be key => value pairs.
Unable to compile generated method %s(): %s
(I) The install_methods subroutine attempted to compile a
subroutine by calling eval on a provided string, which failed for
the indicated reason, usually some type of Perl syntax error.
Unable to dynamically load $package: $%s
(F)
Unable to install code for %s() method: '%s'
(I) The install_methods subroutine was passed an unsupported value
as the code to install for the named method.
Unexpected return value from compilation of %s(): '%s'
(I) The install_methods subroutine attempted to compile a
subroutine by calling eval on a provided string, but the eval
returned something other than than the code ref we expect.
Unexpected return value from meta-method constructor %s: %s
(I) The requested method-generator was invoked, but it returned an
unacceptable value.
EXTENDINGClass::MakeMethods can be extended by creating subclasses that define
additional meta-method types. Callers then select your subclass using
any of the several techniques described above.
Creating A Subclass
The begining of a typical extension might look like the below:
package My::UpperCaseMethods;
use strict;
use Class::MakeMethods '-isasubclass';
sub my_method_type { ... }
You can name your subclass anything you want; it does not need to begin
with Class::MakeMethods.
The '-isasubclass' flag is a shortcut that automatically puts
Class::MakeMethods into your package's @ISA array so that it will
inherit the import() and make() class methods. If you omit this flag,
you will need to place the superclass in your @ISA explicitly.
Typically, the subclass should not inherit from Exporter; both
Class::MakeMethods and Exporter are based on inheriting an import class
method, and getting a subclass to support both would require additional
effort.
Naming Method Types
Each type of method that can be generated is defined in a subroutine of
the same name. You can give your meta-method type any name that is a
legal subroutine identifier.
(Names begining with an underscore, and the names "import" and "make",
are reserved for internal use by Class::MakeMethods.)
If you plan on distributing your extension, you may wish to follow the
"Naming Convention for Generated Method Types" described above to
facilitate reuse by others.
Implementation Options
Each method generation subroutine can be implemented in any one of the
following ways:
· Subroutine Generation
Returns a list of subroutine name/code pairs.
The code returned may either be a coderef, or a string containing
Perl code that can be evaled and will return a coderef. If the eval
fails, or anything other than a coderef is returned, then
Class::MakeMethods croaks.
For example a simple sub-class with a method type
upper_case_get_set that generates an accessor method for each
argument provided might look like this:
package My::UpperCaseMethods;
use Class::MakeMethods '-isasubclass';
sub uc_scalar {
my $class = shift;
map {
my $name = $_;
$name => sub {
my $self = shift;
if ( scalar @_ ) {
$self->{ $name } = uc( shift )
} else {
$self->{ $name };
}
}
} @_;
}
Callers could then generate these methods as follows:
use My::UpperCaseMethods ( 'uc_scalar' => 'foo' );
· Aliasing
Returns a string containing a different meta-method type to use for
those same arguments.
For example a simple sub-class that defines a method type
stored_value might look like this:
package My::UpperCaseMethods;
use Class::MakeMethods '-isasubclass';
sub regular_scalar { return 'Basic::Hash:scalar' }
And here's an example usage:
use My::UpperCaseMethods ( 'regular_scalar' => [ 'foo' ] );
· Rewriting
Returns one or more array references with different meta-method
types and arguments to use.
For example, the below meta-method definition reviews the name of
each method it's passed and creates different types of meta-methods
based on whether the declared name is in all upper case:
package My::UpperCaseMethods;
use Class::MakeMethods '-isasubclass';
sub auto_detect {
my $class = shift;
my @rewrite = ( [ 'Basic::Hash:scalar' ],
[ '::My::UpperCaseMethods:uc_scalar' ] );
foreach ( @_ ) {
my $name_is_uppercase = ( $_ eq uc($_) ) ? 1 : 0;
push @{ $rewrite[ $name_is_uppercase ] }, $_
}
return @rewrite;
}
The following invocation would then generate a regular scalar
accessor method foo, and a uc_scalar method BAR:
use My::UpperCaseMethods ( 'auto_detect' => [ 'foo', 'BAR' ] );
· Generator Object
Returns an object with a method named make_methods which will be
responsible for returning subroutine name/code pairs.
See Class::MakeMethods::Template for an example.
· Self-Contained
Your code may do whatever it wishes, and return an empty list.
Access to Options
Global option values are available through the _context() class method
at the time that method generation is being performed.
package My::Maker;
sub my_methodtype {
my $class = shift;
warn "Installing in " . $class->_context('TargetClass');
...
}
· TargetClass
Class into which code should be installed.
· MakerClass
Which subclass of Class::MakeMethods will generate the methods?
· ForceInstall
Controls whether generated methods will be installed over pre-
existing methods in the target package.
SEE ALSO
License and Support
For distribution, installation, support, copyright and license
information, see Class::MakeMethods::Docs::ReadMe.
Package Documentation
A collection of sample uses is available in
Class::MakeMethods::Docs::Examples.
See the documentation for each family of subclasses:
· Class::MakeMethods::Basic
· Class::MakeMethods::Standard
· Class::MakeMethods::Composite
· Class::MakeMethods::Template
A listing of available method types from each of the different
subclasses is provided in Class::MakeMethods::Docs::Catalog.
Related Modules
For a brief survey of the numerous modules on CPAN which offer some
type of method generation, see
Class::MakeMethods::Docs::RelatedModules.
In several cases, Class::MakeMethods provides functionality closely
equivalent to that of an existing module, and emulator modules are
provided to map the existing module's interface to that of
Class::MakeMethods. See Class::MakeMethods::Emulator for more
information.
If you have used Class::MethodMaker, you will note numerous
similarities between the two. Class::MakeMethods is based on
Class::MethodMaker, but has been substantially revised in order to
provide a range of new features. Backward compatibility and conversion
documentation is provded in Class::MakeMethods::Emulator::MethodMaker.
Perl Docs
See perlboot for a quick introduction to objects for beginners. For an
extensive discussion of various approaches to class construction, see
perltoot and perltootc (called perltootc in the most recent versions of
Perl).
See "Making References" in perlref, point 4 for more information on
closures. (FWIW, I think there's a big opportunity for a "perlfunt"
podfile bundled with Perl in the tradition of "perlboot" and
"perltoot", exploring the utility of function references, callbacks,
closures, and continuations... There are a bunch of useful references
available, but not a good overview of how they all interact in a
Perlish way.)
perl v5.14.2 2004-09-06 MakeMethods(3)
