Module « sqlalchemy.ext.declarative »

Classe « ConcreteBase »

Informations générales

Héritage

builtins.object
    ConcreteBase

Définition

class ConcreteBase(builtins.object):

Description _{[extrait de ConcreteBase.__doc__]}

A helper class for 'concrete' declarative mappings.

    :class:`.ConcreteBase` will use the :func:`.polymorphic_union`
    function automatically, against all tables mapped as a subclass
    to this class.   The function is called via the
    ``__declare_last__()`` function, which is essentially
    a hook for the :meth:`.after_configured` event.

    :class:`.ConcreteBase` produces a mapped
    table for the class itself.  Compare to :class:`.AbstractConcreteBase`,
    which does not.

    Example::

        from sqlalchemy.ext.declarative import ConcreteBase

        class Employee(ConcreteBase, Base):
            __tablename__ = 'employee'
            employee_id = Column(Integer, primary_key=True)
            name = Column(String(50))
            __mapper_args__ = {
                            'polymorphic_identity':'employee',
                            'concrete':True}

        class Manager(Employee):
            __tablename__ = 'manager'
            employee_id = Column(Integer, primary_key=True)
            name = Column(String(50))
            manager_data = Column(String(40))
            __mapper_args__ = {
                            'polymorphic_identity':'manager',
                            'concrete':True}


    The name of the discriminator column used by :func:`.polymorphic_union`
    defaults to the name ``type``.  To suit the use case of a mapping where an
    actual column in a mapped table is already named ``type``, the
    discriminator name can be configured by setting the
    ``_concrete_discriminator_name`` attribute::

        class Employee(ConcreteBase, Base):
            _concrete_discriminator_name = '_concrete_discriminator'

    .. versionadded:: 1.3.19 Added the ``_concrete_discriminator_name``
       attribute to :class:`_declarative.ConcreteBase` so that the
       virtual discriminator column name can be customized.

    .. versionchanged:: 1.4.2 The ``_concrete_discriminator_name`` attribute
       need only be placed on the basemost class to take correct effect for
       all subclasses.   An explicit error message is now raised if the
       mapped column names conflict with the discriminator name, whereas
       in the 1.3.x series there would be some warnings and then a non-useful
       query would be generated.

    .. seealso::

        :class:`.AbstractConcreteBase`

        :ref:`concrete_inheritance`


    

Constructeur(s)

Signature du constructeur	Description
__init__(self, /, *args, **kwargs)	Initialize self. See help(type(self)) for accurate signature. [extrait de __init__.__doc__]

Liste des opérateurs

Opérateurs hérités de la classe object

__eq__, __ge__, __gt__, __le__, __lt__, __ne__

Méthodes héritées de la classe object

__delattr__, __dir__, __format__, __getattribute__, __hash__, __init_subclass__, __reduce__, __reduce_ex__, __repr__, __setattr__, __sizeof__, __str__, __subclasshook__