- New event hook, MapperEvents.after_configured().

    Called after a configure() step has completed and
    mappers were in fact affected.   Theoretically this
    event is called once per application, unless new mappings
    are constructed after existing ones have been used
    already.

  - New declarative features:
        - __declare_last__() method, establishes an event
        listener for the class method that will be called
        when mappers are completed with the final "configure"
        step.
        - __abstract__ flag.   The class will not be mapped
        at all when this flag is present on the class.
        - New helper classes ConcreteBase, AbstractConcreteBase.
        Allow concrete mappings using declarative which automatically
        set up the "polymorphic_union" when the "configure"
        mapper step is invoked.
        - The mapper itself has semi-private methods that allow
        the "with_polymorphic" selectable to be assigned
        to the mapper after it has already been configured.
        [ticket:2239]

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index 3dc1f8676..d778bef3d 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -601,6 +601,9 @@ def has_identity(object):
     return state.has_identity
 
 def _is_mapped_class(cls):
+    """Return True if the given object is a mapped class, 
+    :class:`.Mapper`, or :class:`.AliasedClass`."""
+
     if isinstance(cls, (AliasedClass, mapperlib.Mapper)):
         return True
     if isinstance(cls, expression.ClauseElement):
@@ -610,6 +613,16 @@ def _is_mapped_class(cls):
         return manager and _INSTRUMENTOR in manager.info
     return False
 
+def _mapper_or_none(cls):
+    """Return the :class:`.Mapper` for the given class or None if the 
+    class is not mapped."""
+
+    manager = attributes.manager_of_class(cls)
+    if manager is not None and _INSTRUMENTOR in manager.info:
+        return manager.info[_INSTRUMENTOR]
+    else:
+        return None
+
 def instance_str(instance):
     """Return a string describing an instance."""