UR::Object::Type(3pm)

NAME
UR::Object::Type - a meta-class for any class or primitive type

SYNOPSIS
    use UR;

    class MyClass {
        is => ['ParentClass1', 'ParentClass2'],
        id_by => [
            id_prop1    => { is => 'Integer' },
            id_prop2    => { is => 'String' },
        ],
        has => [
            property_a  => { is => 'String' }
            property_b  => { is => 'Integer', is_optional => 1 },
        ],
    };

    my $meta = MyClass->__meta__;

    my @parent_class_metas = $meta->parents();
    # 2 meta objects, see UR::Object::Property

    my @property_meta = $meta->properties();
    # N properties (4, +1 from UR::Object, +? from ParentClass1 and ParentClass2)

    $meta->is_abstract;

    $meta->...

DESCRIPTION
UR::Object::Type implements the class behind the central metadata in the UR class framework. It contains methods for introspection and manipulation of related class data.

A UR::Object::Type object describes UR::Object, and also every subclass of UR::Object.

INHERITANCE
In addition to describing UR::Object an each of its subclasses, UR::Object::Type is _itself_ a subclass of UR::Object. This means that the same query APIs used for regular objects can be used for meta objects.

   UR::Object  -> has-meta -> UR::Object::Type
          A                         |
          \                        /
           \-----<- is-a  <-------/

Further, new classes which generate a new UR::Objec::Type, also generate a new subclass for the meta-class. This means that each new class can have private meta methods, (ala Ruby).

This means that extensions to a meta-class, apply to the meta-class of its derivatives.

     Regular                    Meta-Class
     Entity                     Singleton
     -------                    ----------

    Greyhound   has-meta ->   Greyhound::Type
        |                          |
        V                          V
      is-a                       is-a
        |                          |
        V                          V
       Dog      has-meta ->    Dog::Type
        |                          |
        V                          V
      is-a                       is-a
        |                          |
        V                          V
      Animal    has-meta ->   Animal::Type
        |                          |
        V                          V
      is-a                       is-a
        |                          |     /-----------------\
        V                          V     V                 |
   UR::Object   has-meta ->   UR::Object::Type   has-meta -/
          A                      is-a
          |                        |
           \______________________/

CONSTRUCTORS

"class"
      class MyClass1 {};

      class MyClass2 { is => 'MyClass1' };

      class MyClass3 {
          is => ['Parent1','Parent2'],
          is_abstract => 1,
          is_transient => 1,
          has => [ qw/p1 p2 p3/ ],
          doc => 'woo hoo!'
      };

    The primary constructor is not a method on this class at all. UR catches "class SOMENAME { ... }" and calls define() with the parameters.

define
      my $class_obj = UR::Object::Type->define(
                          class_name => 'MyClass',
                          ...
                      );

    Register a class with the system. The given class_name must be unique within the application. As a side effect, a new Perl namespace will be created for the class's name, and methods will be injected into that namespace for any of the class properties. Other types of metadata objects will get created to manage the properties and relationships to other classes. See the UR::Object::Type::Initializer documentation for more information about the parameters "define()" accepts.

create
      my $class_obj = UR::Object::Type->create(
                          class_name => 'Namespace::MyClass',
                          ...
                      );

    Create a brand new class within an already existing UR namespace. "create()" takes all the same parameters as "define()". Another side effect of create is that when the application commits its Context, a new Perl module will be created to implement the class, complete with a class definition.

    Applications will not normally use create().

PROPERTIES
Each property has a method of the same name

  External API

class_name
        $name = $class_obj->class_name

    The name of the class. Class names are unique within a UR namespace and an application.

    This is symmetrical with $class_obj = $name->__meta__.

properties
      @all = $class_obj->properties();

      @some = $class_obj->properties(
          'is                    => ['Text','Number']
          'doc like'             => '%important%',
          'property_name like'   => 'someprefix_%',
      );

    Access the related property meta-objects for all properties of this class. It includes the properties of any parent classes which are inherited by this class.

    See UR::Object::Property for details.

property
      $property_meta = $class_obj->property('someproperty');

    The singular version of the above. A single argument, as usual, is treated as the remainder of the ID, and will select a property by name.

namespace
      $namespace_name = $class_obj->namespace

    Returns the name of the class's UR namespace.

doc
      $doc = $class_obj->doc

    A place to put general class-specific notes.

data_source_id
      $ds_id = $class_obj->data_source_id

    The name of the external data source behind this class. Classes without data sources cannot be saved and exist only during the life of the application. data_source_id will resolve to an UR::DataSource id.

table_name
      $table_name = $class_object->table_name

    For classes with data sources, this is the name of the table within that data source. This is usually a table in a relational database.

    At a basic level, it is a storage directive interpreted by the data_source, and may or may not related to a storage table at that level.

is_abstract
      $bool = $class_obj->is_abstract

    A flag indicating if this is an abstract class. Abstract classes cannot have instances, but can be inherited by other classes.

is_final
      $bool = $class_obj->is_final

    A flag indicating if this class cannot have subclasses.

is_singleton
      $bool = $class_obj->is_singleton

    A flag indicating whether this is a singleton class. If true, the class will inherit from UR::Singleton.

is_transactional
      $bool = $class_obj->is_transactional

    A flag indicating whether changes to this class's instances will be tracked. Non-transactional objecs do not change when an in-memory transaction rolls back.

    It is similar to the is_transient meta-property, which does the same for an individual property.

  Internal API
These methods return data about how this class relates to other classes.

namespace_meta
      $ns_meta = $class_obj->namespace_meta

    Returns the UR::Namespace object with the class's namespace name.

parent_class_names
      @names = $class_obj->parent_class_names

    Returns a list of the immediate parent classes.

parent_class_metas
      @class_objs = $class_obj->parent_class_metas

    Returns a list of the class objects (UR::Object::Type instances) of the immediate parent classes

ancestry_class_names
      @names = $class_obj->ancestry_class_names

    Returns a list of all the class names this class inherits from, directly or indirectly. This list may have duplicate names if there is multiple inheritance in the family tree.

ancestry_class_metas
      @class_objs = $class_obj->ancestry_class_metas

    Returns a list of the class objects for each inherited class.

direct_property_names
      @names = $class_obj->direct_property_names

    Returns a list of the property names defined within this class. This list will not include the names of any properties inherited from parent classes unless they have been overridden.

direct_property_metas
      @property_objs = $class_obj->direct_property_metas

    Returns a list of the UR::Object::Property objects for each direct property name.

ancestry_property_names
      @names = $class_obj->ancestry_property_names

    Returns a list of property names of the parent classes and their inheritance hierarchy. The list may include duplicates if a property is overridden somewhere in the hierarchy.

ancestry_property_metas
      @property_objs = $class_obj->ancestry_property_metas;

    Returns a list of the UR::Object::Property objects for each ancestry property name.

all_property_names
    Returns a list of property names of the given class and its inheritance hierarchy. The list may include duplicates if a property is overridden somewhere in the hierarchy.

all_property_metas
      @property_objs = $class_obj->all_property_metas;

    Returns a list of the UR::Object::Property objects for each name returned by all_property_names.

direct_id_property_names
      @names = $class_obj->direct_id_property_names

    Returns a list of the property names designated as "id" properties in the class definition.

direct_id_property_metas
      @property_objs = $class_obj->direct_id_property_metas

    Returns a list of the UR::Object::Property objects for each id property name.

ancestry_id_property_names
ancestry_id_property_metas
all_id_property_names
all_id_property_metas
      @names         = $class_obj->ancestry_id_property_names;
      @property_objs = $class_obj->ancestry_id_property_metas;
      @names         = $class_obj->all_id_property_names;
      @property_objs = $class_obj->all_id_property_metas;

    Returns the property names or UR::Object::Property objects for either the parent classes and their inheritance hierarchy, or for the given class and all of its inheritance hierarchy. The lists may include duplicates if properties are overridden somewhere in the hierarchy.

unique_property_set_hashref
      $constraints = $class_obj->unique_property_set_hashref

    Return a hashref describing the unique constraints on the given class. The keys of $constraint are constraint names, and the values are listrefs of property names that make up the unique constraint.

add_unique_constraint
      $class_obj->add_unique_constraint($constraint_name, @property_name_list)

    Add a unique constraint to the given class. It is an exception if the given $constraint_name already exists as a constraint on this class or its parent classes.

remove_unique_constraint
      $class_obj->remove_unique_constraint($constraint_name)

    Remove a unique constraint from the given class. It is an exception if the given constraint name does not exist.

ancestry_table_names
all_table_names
      @names = $class_obj->ancestry_table_names

    Returns a list of table names in the class's inheritance hierarchy.

direct_column_names
    Returns a list of column names for each direct property meta. Classes with data sources and table names will have properties with column names.

direct_id_column_names
    Returns a list of ID column names for each direct property meta.

direct_columnless_property_names
direct_columnless_property_metas
ancestry_columnless_property_names
ancestry_columnless_property_metas
all_columnless_property_names
all_columnless_property_metas
    Return lists of property meta objects and their names for properties that have no column name.

METHODS

property_meta_for_name
      $property_obj = $class_obj->property_meta_for_name($property_name);

    Return the UR::Object::Property object in the class's inheritance hierarchy with the given name. If the property name has been overridden somewhere in the hierarchy, then it will return the property object most specific to the class.

id_property_sorter
      $subref = $class_obj->id_property_sorter;
      @sorted_objs = sort $subref @unsorted_objs;

    Returns a subroutine reference that can be used to sort object instances of the class. The subref is able to handle classes with multiple ID properties, and mixes of numeric and non-numeric data and data types.

autogenerate_new_object_id
    This method is called whenever new objects of the given class are created through "ClassName->create()", and not all of their ID properties were specified. UR::Object::Type has an implementation used by default, but other classes can override this if they need special handling.

singular_accessor_name_for_is_many_accessor
      $property_name = $class_obj->singular_accessor_name_for_is_many_accessor($is_many_name);

    For is_many properties, returns the name of the singular accessor. Usually, this the singular version of the plural, is_many property's name. The singular accessor accepts key/value pairs as arguments, which are used to filter the results of the is_many accessor. For example, the singular for the 'cars' accessor is 'car'.

    Returns a false value if the given property name does not exist or is not is_many.

iterator_accessor_name_for_is_many_accessor
      $iter_name = $class_obj->iterator_accessor_name_for_is_many_accessor($is_many_name);

    Returns the accessor name used to get the UR::Object::Iterator that corresponds with the is_many accessor. For example, the iterator for the 'cars' accessor is 'car_iterator'.

    Returns a false value if the given property name does not exist or is not is_many.

set_accessor_name_for_is_many_accessor
      $set_name = $class_obj->set_accessor_name_for_is_many_accessor($is_many_name);

    Returns the accessor name used to get the UR::Object::Set that corresponds with the is_many accessor. For example, the set for the 'cars' accessor is 'car_set'.

    Returns a false value if the given property name does not exist or is not is_many.

rule_accessor_name_for_is_many_accessor
      $rule_name = $class_obj->rule_accessor_name_for_is_many_accessor($is_many_name);

    Returns the accessor name used to get the UR::BoolExpr that corresponds with the is_many accessor. For example, the rule for the 'cars' accessor is '__car_rule'.

    Returns a false value if the given property name does not exist or is not is_many.

arrayref_accessor_name_for_is_many_accessor
      $arrayref_name = $class_obj->arrayref_accessor_name_for_is_many_accessor($is_many_name);

    Returns the accessor name used to get the arrayref of objects that corresponds with the is_many accessor. For example, the arrayref for the 'cars' accessor is 'car_arrayref'.

    Returns a false value if the given property name does not exist or is not is_many.

adder_name_for_is_many_accessor
      $adder_name = $class_obj->adder_name_for_is_many_accessor($is_many_name);

    Returns the method name used to get the adder method that corresponds with the is_many accessor. For example, the adder for the 'cars' accessor is 'add_car'.

    Returns a false value if the given property name does not exist or is not is_many.

remover_name_for_is_many_accessor
      $remover_name = $class_obj->remover_name_for_is_many_accessor($is_many_name);

    Returns the method name used to get the remover method that corresponds with the is_many accessor. For example, the adder for the 'cars' accessor is 'remove_car'.

    Returns a false value if the given property name does not exist or is not is_many.

SEE ALSO
UR::Object::Property, UR::Object::Iterator, UR::Object::Set, UR::BoolExpr