Inheritance SQLAlchemy和带backrefs的多态性继承
我有如下所示的类Inheritance SQLAlchemy和带backrefs的多态性继承,inheritance,sqlalchemy,flask-sqlalchemy,polymorphism,backreference,Inheritance,Sqlalchemy,Flask Sqlalchemy,Polymorphism,Backreference,我有如下所示的类Node和Leaf(Node):它工作正常,但我更愿意将leafs和subbafs定义转移到Leaf(Node)类。我如何做到这一点 class Node (db.Model): __mapper_args__ = {'polymorphic_identity':'node', 'polymorphic_on':'type'} id = db.Column (db.Integer, primary_key=True) type = db.Column ('
Node
和Leaf(Node)
:它工作正常,但我更愿意将leafs
和subbafs
定义转移到Leaf(Node)
类。我如何做到这一点
class Node (db.Model):
__mapper_args__ = {'polymorphic_identity':'node', 'polymorphic_on':'type'}
id = db.Column (db.Integer, primary_key=True)
type = db.Column ('type', db.String (16))
root_id = db.Column (db.Integer, db.ForeignKey (id))
nodes = db.relationship ('Node',
cascade='all', lazy='dynamic',
primaryjoin='Node.root_id==Node.id',
backref=db.backref('root', remote_side=id))
leafs = db.relationship ('Leaf',
cascade='all', lazy='dynamic',
primaryjoin='Leaf.root_id==Node.id')
base_id = db.Column (db.Integer, db.ForeignKey (id))
subnodes = db.relationship ('Node',
cascade='all', lazy='dynamic',
primaryjoin='Node.base_id==Node.id',
backref=db.backref('base', remote_side=id))
subleafs = db.relationship ('Leaf',
cascade='all', lazy='dynamic',
primaryjoin='Leaf.base_id==Node.id')
def __init__ (self, root):
self.base = root.base if root and root.base else root
self.root = root
及
我尝试了这个,但失败了(部分):
我的delete测试用例不喜欢这样(只是删除树中的基本/根节点并依赖cascade='all'
),并抱怨:
CircularDependencyError: Circular dependency detected. Cycles: set([DeleteState(<Leaf at 0x22789d0>)]) all edges: set([(DeleteState(<Leaf at 0x22789d0>), DeleteState(<Leaf at 0x22789d0>))])
我想我需要使用
Leaf(Node)
中的某些内容来附加关系,即使我在Node
中的leafs
和subleafs
的原始定义中不需要使用任何backref。Thx.好吧,在尝试了一些之后,我找到了一个解决方案,这不是完美的,但是完成了工作:我只是将节点。leafs
和节点。subbafs
定义移动到文件leaf.py
中,其中定义了类叶(节点)
,并附加了前面的定义,如下所示:
class Leaf (Node):
__mapper_args__ = {'polymorphic_identity': 'leaf'}
leaf_id = db.Column (db.Integer, db.ForeignKey ('node.id'), primary_key=True)
def __init__ (self, root):
super (Leaf, self).__init__ (root)
Node.leafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.root_id)
Node.subleafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.base_id)
这样做的一个缺点是,如果人们想访问节点.leafs
和节点.subleafs
,就必须从模型导入Leaf,但由于他们无论如何都必须这样做(即使节点.leafs
和节点.subleafs
在类叶(节点)
中被定义为backrefs),没关系
如果有人找到了一个解决方案,其中关系被定义为
类叶(节点)
中的backrefs,我很高兴听到您的消息;thx.好吧,在尝试了一些之后,我找到了一个解决方案,这不是完美的,但是完成了工作:我只是将节点。leafs
和节点。subbafs
定义移动到文件leaf.py
中,其中定义了类叶(节点)
,并附加了前面的定义,如下所示:
class Leaf (Node):
__mapper_args__ = {'polymorphic_identity': 'leaf'}
leaf_id = db.Column (db.Integer, db.ForeignKey ('node.id'), primary_key=True)
def __init__ (self, root):
super (Leaf, self).__init__ (root)
Node.leafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.root_id)
Node.subleafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.base_id)
这样做的一个缺点是,如果人们想访问节点.leafs
和节点.subleafs
,就必须从模型导入Leaf,但由于他们无论如何都必须这样做(即使节点.leafs
和节点.subleafs
在类叶(节点)
中被定义为backrefs),没关系
如果有人找到了一个解决方案,其中关系被定义为类叶(节点)
中的backrefs,我很高兴听到您的消息;thx
AttributeError: 'Node' object has no attribute 'leafs'
class Leaf (Node):
__mapper_args__ = {'polymorphic_identity': 'leaf'}
leaf_id = db.Column (db.Integer, db.ForeignKey ('node.id'), primary_key=True)
def __init__ (self, root):
super (Leaf, self).__init__ (root)
Node.leafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.root_id)
Node.subleafs = db.relationship (Leaf, cascade='all', lazy='dynamic',
primaryjoin=Node.id==Leaf.base_id)