我在一个相当简单的情况下有映射问题。有人可以帮忙吗？ 以下是DTO：
class AttributeDTO(object):
id = None
name = None
class RelationDTO(object):
id = None
name = None
attribute = None # one attribute per relation
class EntityDTO(object):
id = None
name = None
relation = None
#it works fine, but then I must get myEnt.relation.attribute,
#when i want to get the attribute from entity
attribute = None # I want it to be placed HERE!
以下是地图制作者：
class TableMapper(object):
def __init__(self, metadata, mapped_type):
self._table = None
self._mapped_type = mapped_type
def get_table(self):
return self._table
def set_table(self, table):
self._table = table
def map_table(self):
mapper(self._mapped_type, self._table)
return self._table
class AttributeTableMapper(TableMapper):
...
class RelationTableMapper(TableMapper):
...
def map_table(self, attribute_table):
r_attribute = relationship(AttributeDTO,
uselist = False, remote_side = [attribute_table.c.id])
mapper(RelationDTO,
self._table,
properties = {'attribute': r_attribute})
return self._table
class EntityTableMapper(TableMapper):
def __init__(self, metadata):
TableMapper.__init__(self, metadata, EntityDTO)
self.set_table(Table('entities', metadata,
Column('id', Integer, ...)))
def map_table(self, relation_table, attribute_table):
r_attribute = relationship(AtributeDTO, uselist = False,
#I TRIED THE FOLLOWING, BUT GOT ERRORS
#!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
primaryjoin = self._table.c.id_relation == relation.c.id,
secondary = relation_table,
secondaryjoin = relation_table.c.id_attribute == attribute_table.c.id)
#!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
mapper(EntityDTO, self._table, properties={'attribute': r_attribute})
return self._table
所以，我映射表格：
attribute_t_mapper = AttributeTableMapper(self._metadata)
relation_table = RelationTableMapper(self._metadata).\
map_table(attribute_t_mapper.get_table())
attribute_table = attribute_t_mapper.map_table()
entity_table = EntityTableMapper(self._metadata).\
map_table(relation_table, attribute_table)
并尝试从实体获取我的属性：
entity = session.query(EntityDTO).first() #OK!
a = entity.relation.attribute #OK!
a = entity.attribute #ERROR!
sqlalchemy.orm.exc.UnmappedColumnError：没有在mapper Mapper | EntityDTO |实体上配置列relation.id ...
我做错了什么？