我有两个模型:
class Project(db.Model):
__tablename__ = 'project'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(64))
timestamp = db.Column(db.DateTime)
info = db.Column(db.Text(255))
post = db.relationship('Post', backref=db.backref('projects'))
class Post(db.Model):
__tablename__ = 'post'
id = db.Column(db.Integer, primary_key=True)
headline = db.Column(db.String(64))
content = db.Column(db.Text(255))
timestamp = db.Column(db.DateTime)
projectId = db.Column(db.Integer, db.ForeignKey('project.id'))
例如,如果我创建了一个post实例,然后通过projectInstance.append(post(headline="...", content="..."))
Now将其附加到项目中,那么我想更新post应该属于的项目。除了查询所需的项目,将帖子附加到该项目并将其从旧项目中删除,还有没有更简单的方法?
oldProject.remove(post)
newProject.append(post)
用另一种方法来做:在中使用back引用Post
:
post.projects = newProject
这将处理所需的会话管理。这是一个最小的示例:
In [2]: class A(Base):
...: __tablename__ = 'a'
...: id = Column(Integer, primary_key=True, autoincrement=True)
...: bs = relationship('B', backref='a')
...:
In [3]: class B(Base):
...: __tablename__ = 'b'
...: id = Column(Integer, primary_key=True, autoincrement=True)
...: a_id = Column(Integer, ForeignKey('a.id'))
...:
In [5]: a1 = A()
In [6]: a2 = A()
In [7]: b = B()
In [8]: a1.bs.append(b)
In [9]: a1.bs
Out[9]: [<__main__.B at 0x7f7322fb52b0>]
In [10]: b.a = a2
In [11]: a1.bs, a2.bs
Out[11]: ([], [<__main__.B at 0x7f7322fb52b0>])
同样,只需将post
实例附加到newProject.post
集合句柄即可自动删除,如我们的as和bs所示:
In [9]: a1.bs.append(b)
In [10]: a1.bs, a2.bs
Out[10]: ([<__main__.B at 0x7f26702565f8>], [])
In [11]: a2.bs.append(b)
In [12]: a1.bs, a2.bs
Out[12]: ([], [<__main__.B at 0x7f26702565f8>])
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我来说两句