Module « sqlalchemy.orm »

Fonction synonym - module sqlalchemy.orm

Signature de la fonction synonym

def synonym(name, map_column=None, descriptor=None, comparator_factory=None, doc=None, info=None) 

Description

synonym.__doc__

Denote an attribute name as a synonym to a mapped property,
        in that the attribute will mirror the value and expression behavior
        of another attribute.

        e.g.::

            class MyClass(Base):
                __tablename__ = 'my_table'

                id = Column(Integer, primary_key=True)
                job_status = Column(String(50))

                status = synonym("job_status")


        :param name: the name of the existing mapped property.  This
          can refer to the string name ORM-mapped attribute
          configured on the class, including column-bound attributes
          and relationships.

        :param descriptor: a Python :term:`descriptor` that will be used
          as a getter (and potentially a setter) when this attribute is
          accessed at the instance level.

        :param map_column: **For classical mappings and mappings against
          an existing Table object only**.  if ``True``, the :func:`.synonym`
          construct will locate the :class:`_schema.Column`
          object upon the mapped
          table that would normally be associated with the attribute name of
          this synonym, and produce a new :class:`.ColumnProperty` that instead
          maps this :class:`_schema.Column`
          to the alternate name given as the "name"
          argument of the synonym; in this way, the usual step of redefining
          the mapping of the :class:`_schema.Column`
          to be under a different name is
          unnecessary. This is usually intended to be used when a
          :class:`_schema.Column`
          is to be replaced with an attribute that also uses a
          descriptor, that is, in conjunction with the
          :paramref:`.synonym.descriptor` parameter::

            my_table = Table(
                "my_table", metadata,
                Column('id', Integer, primary_key=True),
                Column('job_status', String(50))
            )

            class MyClass(object):
                @property
                def _job_status_descriptor(self):
                    return "Status: %s" % self._job_status


            mapper(
                MyClass, my_table, properties={
                    "job_status": synonym(
                        "_job_status", map_column=True,
                        descriptor=MyClass._job_status_descriptor)
                }
            )

          Above, the attribute named ``_job_status`` is automatically
          mapped to the ``job_status`` column::

            >>> j1 = MyClass()
            >>> j1._job_status = "employed"
            >>> j1.job_status
            Status: employed

          When using Declarative, in order to provide a descriptor in
          conjunction with a synonym, use the
          :func:`sqlalchemy.ext.declarative.synonym_for` helper.  However,
          note that the :ref:`hybrid properties <mapper_hybrids>` feature
          should usually be preferred, particularly when redefining attribute
          behavior.

        :param info: Optional data dictionary which will be populated into the
            :attr:`.InspectionAttr.info` attribute of this object.

            .. versionadded:: 1.0.0

        :param comparator_factory: A subclass of :class:`.PropComparator`
          that will provide custom comparison behavior at the SQL expression
          level.

          .. note::

            For the use case of providing an attribute which redefines both
            Python-level and SQL-expression level behavior of an attribute,
            please refer to the Hybrid attribute introduced at
            :ref:`mapper_hybrids` for a more effective technique.

        .. seealso::

            :ref:`synonyms` - Overview of synonyms

            :func:`.synonym_for` - a helper oriented towards Declarative

            :ref:`mapper_hybrids` - The Hybrid Attribute extension provides an
            updated approach to augmenting attribute behavior more flexibly
            than can be achieved with synonyms.