# Class::MOP::Instance - phpMan ## NAME [Class::MOP::Instance] - Instance Meta Object ## VERSION version 2.2200 ## DESCRIPTION The Instance Protocol controls the creation of object instances, and the storage of attribute values in those instances. Using this API directly in your own code violates encapsulation, and we recommend that you use the appropriate APIs in [Class::MOP::Class] and [Class::MOP::Attribute] instead. Those APIs in turn call the methods in this class as appropriate. This class also participates in generating inlined code by providing snippets of code to access an object instance. ## METHODS Object construction [Class::MOP::Instance]->new(%options) This method creates a new meta-instance object. It accepts the following keys in %options: * associated_metaclass The [Class::MOP::Class] object for which instances will be created. * attributes An array reference of [Class::MOP::Attribute] objects. These are the attributes which can be stored in each instance. Creating and altering instances $metainstance->create_instance This method returns a reference blessed into the associated metaclass's class. The default is to use a hash reference. Subclasses can override this. $metainstance->clone_instance($instance) Given an instance, this method creates a new object by making *shallow* clone of the original. Introspection $metainstance->associated_metaclass This returns the [Class::MOP::Class] object associated with the meta-instance object. $metainstance->get_all_slots This returns a list of slot names stored in object instances. In almost all cases, slot names correspond directly attribute names. $metainstance->is_valid_slot($slot_name) This will return true if $slot_name is a valid slot name. $metainstance->get_all_attributes This returns a list of attributes corresponding to the attributes passed to the constructor. Operations on Instance Structures It's important to understand that the meta-instance object is a different entity from the actual instances it creates. For this reason, any operations on the $instance_structure always require that the object instance be passed to the method. $metainstance->get_slot_value($instance_structure, $slot_name) $metainstance->set_slot_value($instance_structure, $slot_name, $value) $metainstance->initialize_slot($instance_structure, $slot_name) $metainstance->deinitialize_slot($instance_structure, $slot_name) $metainstance->initialize_all_slots($instance_structure) $metainstance->deinitialize_all_slots($instance_structure) $metainstance->is_slot_initialized($instance_structure, $slot_name) $metainstance->weaken_slot_value($instance_structure, $slot_name) $metainstance->slot_value_is_weak($instance_structure, $slot_name) $metainstance->strengthen_slot_value($instance_structure, $slot_name) $metainstance->rebless_instance_structure($instance_structure, $new_metaclass) The exact details of what each method does should be fairly obvious from the method name. Inlinable Instance Operations $metainstance->is_inlinable This is a boolean that indicates whether or not slot access operations can be inlined. By default it is true, but subclasses can override this. $metainstance->inline_create_instance($class_variable) This method expects a string that, *when inlined*, will become a class name. This would literally be something like '$class', not an actual class name. It returns a snippet of code that creates a new object for the class. This is something like " bless {}, $class_name ". $metainstance->inline_get_is_lvalue Returns whether or not "inline_get_slot_value" is a valid lvalue. This can be used to do extra optimizations when generating inlined methods. $metainstance->inline_slot_access($instance_variable, $slot_name) $metainstance->inline_get_slot_value($instance_variable, $slot_name) $metainstance->inline_set_slot_value($instance_variable, $slot_name, $value) $metainstance->inline_initialize_slot($instance_variable, $slot_name) $metainstance->inline_deinitialize_slot($instance_variable, $slot_name) $metainstance->inline_is_slot_initialized($instance_variable, $slot_name) $metainstance->inline_weaken_slot_value($instance_variable, $slot_name) $metainstance->inline_strengthen_slot_value($instance_variable, $slot_name) These methods all expect two arguments. The first is the name of a variable, than when inlined, will represent the object instance. Typically this will be a literal string like '$_[0]'. The second argument is a slot name. The method returns a snippet of code that, when inlined, performs some operation on the instance. $metainstance->inline_rebless_instance_structure($instance_variable, $class_variable) This takes the name of a variable that will, when inlined, represent the object instance, and the name of a variable that will represent the class to rebless into, and returns code to rebless an instance into a class. Introspection [Class::MOP::Instance]->meta This will return a [Class::MOP::Class] instance for this class. It should also be noted that [Class::MOP] will actually bootstrap this module by installing a number of attribute meta-objects into its metaclass. ## AUTHORS * Stevan Little <> * Dave Rolsky <> * Jesse Luehrs <> * Shawn M Moore <> * יובל קוג'מן (Yuval Kogman) <> * Karen Etheridge <> * Florian Ragwitz <> * Hans Dieter Pearcey <> * Chris Prather <> * Matt S Trout <> ## COPYRIGHT AND LICENSE This software is copyright (c) 2006 by Infinity Interactive, Inc. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.