Anthony Brummett > UR-0.41 > UR::Object::Type



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


    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)



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.


Each sub-class of UR::Object has a single UR::Object::Type object describing the class. The UR::Object class itself also has a UR::Object::Type object describing the base class of the system.

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

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

This also 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
            |                          |


  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.

  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.

  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().


Each property has a method of the same name

External API

    $name = $class_obj->class_name

The full name of the class. This is symmetrical with $class_obj = $name->__meta__.

  @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.

  @all_id = $class_obj->id_properties();

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

Like properties(), but only returns ID property metadata.

  $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.

  @names = $class_obj->property_names;

Returns a list of all properties belonging to the class, directly or through inheritance.

  $namespace_name = $class_obj->namespace

Returns the name of the class's UR namespace.

  $doc = $class_obj->doc

A place to put general class-specific notes.

  $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 = $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.

  $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.

  $bool = $class_obj->is_final

A flag indicating if this class cannot have subclasses.

  $bool = $class_obj->is_singleton

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

  $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.

  $ns_meta = $class_obj->namespace_meta

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

  @names = $class_obj->parent_class_names

Returns a list of the immediate parent classes.

  @class_objs = $class_obj->parent_class_metas

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

  @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.

  @class_objs = $class_obj->ancestry_class_metas

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

  @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.

  @property_objs = $class_obj->direct_property_metas

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

  @names = $class_obj->ancestry_property_names

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

  @property_objs = $class_obj->ancestry_property_metas;

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


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

  @property_objs = $class_obj->all_property_metas;

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

  @names = $class_obj->direct_id_property_names

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

  @property_objs = $class_obj->direct_id_property_metas

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

  @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 heirarchy, or for the given class and all of its inheritance heirarchy. The lists may include duplicates if properties are overridden somewhere in the heirarchy.

  $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.

  $class_obj->add_unique_constraint($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 a unique constraint from the given class. It is an exception if the given constraint name does not exist.

  @names = $class_obj->ancestry_table_names

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


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


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


Return lists of property meta objects and their names for properties that have no column 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.

  $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.


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.



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