Object::Pad::MOP::Class(3pm)

NAME
"Object::Pad::MOP::Class" - meta-object representation of a "Object::Pad" class

DESCRIPTION
Instances of this class represent a class or role implemented by Object::Pad. Accessors provide information about the class or role, and methods that can alter the class, typically by adding new elements to it, allow a program to extend existing classes.

Where possible, this API is designed to be compatible with MOP::Class.

This API should be considered experimental, and will emit warnings to that effect. They can be silenced with

   use Object::Pad qw( :experimental(mop) );

or

   use Object::Pad::MOP::Class qw( :experimental(mop) );

CONSTRUCTOR

  for_class
   $metaclass = Object::Pad::MOP::Class->for_class( $class );

Since version 0.38.

Returns the metaclass instance associated with the given class name. Throws an exception if the requested class is not using "Object::Pad".

  try_for_class
   $metaclass = Object::Pad::MOP::Class->try_for_class( $class );

Since version 0.808.

If the given class name is built using "Object::Pad" then returns the metaclass instance for it. If not, returns "undef".

  for_caller
   $metaclass = Object::Pad::MOP::Class->for_caller;

Since version 0.38.

A convenient shortcut for obtaining the metaclass instance of the calling package scope. Often handy during "BEGIN" blocks of the class itself to perform adjustments or additions.

   class Some::Class::Here 1.234 {
      BEGIN {
         my $meta = Object::Pad::MOP::Class->for_caller;
         ...
      }
   }

  create_class
   my $metaclass = Object::Pad::MOP::Class->create_class( $name, %args );

Since version 0.61.

Creates a new class of the given name and yields the metaclass for it.

Takes the following additional named arguments:

extends => STRING
isa => STRING
    An optional name of a superclass that this class will extend. These options are synonyms; new code should use "isa", as "extends" will eventually be removed.

abstract => BOOL
    Optionally; if given a true value the newly-created class will be declared as abstract, as if the ":abstract" attribute had been applied.

Once created, this metaclass must be sealed using the "seal" method before it can be used to actually construct object instances.

  create_role
   my $metaclass = Object::Pad::MOP::Class->create_role( $name, %args );

Since version 0.61.

As "create_class" but creates a role instead of a class.

  begin_class
   BEGIN {
      my $metaclass = Object::Pad::MOP::Class->begin_class( $name, %args );
      ...
   }

Since version 0.46.

A variant of "create_class" which sets the newly-created class as the current complication scope of the surrounding code, allowing it to accept "Object::Pad" syntax forms such as "has" and "method".

This must be done during "BEGIN" time because of this compiletime effect. It additionally creates a deferred code block at "UNITCHECK" time of its surrounding scope, which is used to finalise the constructed class. In this case you do not need to remember to call "seal" on it; this happens automatically.

  begin_role
Since version 0.46.

As "begin_class" but creates a role instead of a class.

METHODS

  is_class

  is_role
   $bool = $metaclass->is_class;
   $bool = $metaclass->is_role;

Exactly one of these methods will return true, depending on whether this metaclass instance represents a true "class", or a "role".

  is_abstract
   $bool = $metaclass->is_abstract;

True on a "role", or a "class" that was declared with the ":abstract" attribute.

  name
   $name = $metaclass->name;

Returns the name of the class, as a plain string.

  superclasses
   @classes = $metaclass->superclasses;

Returns a list of superclasses, as Object::Pad::MOP::Class instances.

Because "Object::Pad" does not support multiple superclasses, this list will contain at most one item.

  direct_roles
   @roles = $metaclass->direct_roles;

Returns a list of the roles introduced by this class (i.e. added by `does` declarations but not inherited from the superclass), as Object::Pad::MOP::Class instances.

This method is also aliased as "roles".

  all_roles
   @roles = $metaclass->all_roles;

Since version 0.56.

Returns a list of all the roles implemented by this class (i.e. including those inherited from the superclass), as Object::Pad::MOP::Class instances.

  add_role
   $metaclass->add_role( $rolename );
   $metaclass->add_role( $rolemeta );

Since version 0.56.

Adds a new role to the list of those implemented by the class.

The new role can be specified either as a plain string giving its name, or as an "Object::Pad::MOP::Class" meta instance directly.

Before version 0.56 this was called "compose_role".

  add_BUILD
   $metaclass->add_BUILD( $code );

Adds a new "BUILD" block to the class, as a CODE reference.

  add_method
   $metamethod = $metaclass->add_method( $name, %args, $code );

Adds a new named method to the class under the given name, as CODE reference.

Returns an instance of Object::Pad::MOP::Method to represent it.

Recognises the following additional named arguments:

common => BOOL
    Since version 0.62.

    If true, the method is a class-common method.

  get_direct_method
   $metamethod = $metaclass->get_direct_method( $name );

Returns an instance of Object::Pad::MOP::Method to represent the method of the given name, if one exists. If not an exception is thrown.

This can only see directly-applied methods; that is, methods created by the "method" keyword on the class itself, or added via "add_method". This will not see other names in the package stash, even if they contain a "CODE" slot, nor will it see methods inherited from a superclass.

This is also aliased as "get_own_method" for compatibility with the MOP::Class interface.

  get_method
   $metamethod = $metaclass->get_method( $name );

Since version 0.57.

Returns an instance of Object::Pad::MOP::Method to represent the method of the given name, if one exists. If not an exception is thrown.

This will additionally search superclasses, and may return a method belonging to a parent class.

  direct_methods
   @metamethods = $metaclass->direct_methods;

Since version 0.57.

Returns a list of Object::Pad::MOP::Method instances to represent all the direct methods of the class. This list may be empty.

  all_methods
   @metamethods = $metaclass->all_methods;

Since version 0.57.

Returns a list of Object::Pad::MOP::Method instances to represent all the methods of the class, including those inherited from superclasses. This list may be empty.

  add_field
   $metafield = $metaclass->add_field( $name, %args );

since version 0.60.

Adds a new field to the class, using the given name (which must begin with the sigil character "$", "@" or "%").

Recognises the following additional named arguments:

default => SCALAR
    Since version 0.43.

    Provides a default value for the field; similar to using the syntax

       has $field = SCALAR;

    This value may be "undef", to set the value as being optional if it additionally has a parameter name.

param => STRING
    Since version 0.43.

    Provides a parameter name for the field; similar to setting it using the ":param" attribute. This parameter will be required unless a default value is set (such value may still be "undef").

reader => STRING
writer => STRING
mutator => STRING
    Since version 0.46.

accessor => STRING
    Since version 0.56.

    Provides method names for generated reader, writer, lvalue-mutator or reader+writer accessor methods, similar to setting them via the ":reader", ":writer", ":mutator" or ":accessor" attributes.

weak => BOOL
    Since version 0.46.

    If true, reference values assigned into the field by the constructor or accessor methods will be weakened, similar to setting the ":weak" attribute.

attributes => ARRAY
    Since version 0.811.

    Provides additional attributes to apply to the field, as if declared by attribute syntax. This is largely useful for applying third-party field attributes.

    The referenced array should contain an even-sized list of pairs. The first of each pair will be the name of an attribute, and the second will be a value to pass (or "undef" if not applicable). Note that if the third-party attribute provides separate parse and apply phases in its hook functions, the parse part will not be invoked by this parameter. Whatever value is passed must be something accepted by the apply phase alone.

Returns an instance of Object::Pad::MOP::Field to represent it.

  add_slot
   $metafield = $metaclass->add_slot( $name, %args );

Now deprecated.

Back-compatibility alias for "add_field".

  get_field
   $metafield = $metaclass->get_field( $name );

Since version 0.60.

Returns an instance of Object::Pad::MOP::Field to represent the field of the given name, if one exists. If not an exception is thrown.

  get_slot
   $metafield = $metaclass->get_slot( $name );

Now deprecated.

Back-compatibility alias for "get_field".

  fields
   @metafields = $metaclass->fields;

Since version 0.60.

Returns a list of Object::Pad::MOP::Field instances to represent all the fields of the class. This list may be empty.

  slots
   @metafields = $metaclass->slots;

Since version 0.42; now deprecated.

Back-compatibility alias for "fields".

  add_required_method
   $metaclass->add_required_method( $name );

Since version 0.61.

Adds a new required method to the role, whose name is given as a plain string.

Currently returns nothing. This should be considered temporary, as eventually a metatype for required methods will be added, at which point this method can return instances of it. It may also take additional parameters to define the required method with. Currently extra parameters are not permitted.

  required_method_names
   @names = $metaclass->required_method_names;

Since version 0.61.

Returns a list names of required methods for the role, as plain strings.

This should be considered a temporary method. Currently there is no metatype for required methods, so they are represented as plain strings. Eventually a type may be defined and a "required_methods" method will be added.

  seal
   $metaclass->seal;

Since version 0.61.

If the metaclass was created by "create_class" or "create_role", this method must be called once everything has been added into it, as the class will not yet be ready to construct actual object instances before this is done.

AUTHOR
Paul Evans <leonerd@leonerd.org.uk>