我正在尝试使用SQLAlchemy和Flask重新创建我的数据库。
我已经创建了所有的模型，但现在模型之间的关系出现了一些问题。插入或更新对象时，Flask返回以下错误消息：
File "C:UsersLennaSchoolMiapi-server-v4venvlibsite-packagessqlalchemyextdeclarativeclsregistry.py", line 326, in __call__
x = eval(self.arg, globals(), self._dict)
File "<string>", line 1, in <module>
# ext/declarative/clsregistry.py
AttributeError: 'Table' object has no attribute 'id'
错误消息引用配置文件类中的active_channel关系，并指示通道类没有id属性。但是，我已经在ObjectWithDefaultProps类中定义了这个属性。在SQL浏览器中检查SQL文件后，Channel实体上确实存在id属性。
我的第一个假设是foreignkey的错误配置，所以我试图更改foreignkey：
active_channel = db.relationship("Channel", foreign_keys="Channel.id")
而不是
active_channel = db.relationship("Channel", foreign_keys="channel.id")
不幸的是，这并没有奏效。错误更改为以下内容：
sqlalchemy.exc.NoForeignKeysError: Could not determine join condition between parent/child tables on
relationship Profile.active_channel - there are no foreign keys linking these tables. Ensure that referencing
columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression. //
Werkzeug Debugger
我已经深入研究了SQLAlchemy的多态性方面，并认为它可能与映射器参数有关，但无法找到实现这一点的正确方法。
在我的代码中，我有以下类：
我的实体派生自多个对象，这些对象表示共享属性或关系。
class Profile(db.Model, ObjectWithDefaultProps, ObjectWithAvatar, ObjectWithNotificationProfile):
__tablename__ = "profile"
firebase_uid = db.Column(db.String, unique=True, nullable=False, primary_key=True)
username = db.Column(db.String, unique=True, nullable=False)
firstname = db.Column(db.String, nullable=False)
lastname = db.Column(db.String, nullable=False)
about = db.Column(db.String)
score = db.Column(db.Integer)
email = db.Column(db.String, nullable=False)
active_channel_id = db.Column(db.Integer, db.ForeignKey("channel.id"))
active_channel = db.relationship("Channel", foreign_keys="channel.id")
信道.py
class Channel(db.Model, ObjectBase, ObjectWithAvatar, ObjectWithName, ProfileLinkedObject):
__tablename__ = "channel"
description = db.Column(db.String)
can_add_tags = db.Column(db.Boolean, default=False, nullable=False)
can_public_join = db.Column(db.Boolean, default=False, nullable=False)
from database.provider import db
from datetime import datetime
class ObjectWithDefaultProps:
deleted = db.Column(db.Boolean, nullable=False, default=False)
date_modified = db.Column(db.DateTime, default=datetime.utcnow)
date_added = db.Column(db.DateTime, onupdate=datetime.utcnow)
from database.provider import db
from database.extensions.object_with_color import ObjectWithColor
class ObjectWithAvatar(ObjectWithColor):
image_url = db.Column(db.String)
from database.provider import db
class ObjectWithColor:
color_index = db.Column(db.Integer, default=0)
from database.provider import db
from sqlalchemy.ext.declarative import declared_attr
class ObjectWithNotificationProfile:
auto_follow_questions = db.Column(db.Integer)
auto_follow_answers = db.Column(db.Integer)
auto_follow_comments = db.Column(db.Integer)
auto_follow_questions_on_comment = db.Column(db.Integer)
auto_follow_questions_on_answer = db.Column(db.Integer)
auto_follow_answers_on_comment = db.Column(db.Integer)
send_new_data_notification = db.Column(db.Boolean)
send_new_members_notification = db.Column(db.Boolean)
@declared_attr
def question_event_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_event_preferences.id"))
@declared_attr
def question_event_preferences(cls):
return db.relationship("CustomEventPreferences", foreign_keys="custom_event_preferences.id")
@declared_attr
def answer_event_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_event_preferences.id"))
@declared_attr
def answer_event_preferences(cls):
return db.relationship("CustomEventPreferences", foreign_keys="custom_event_preferences.id")
@declared_attr
def comment_event_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_event_preferences.id"))
@declared_attr
def comment_event_preferences(cls):
return db.relationship("CustomEventPreferences", foreign_keys="custom_event_preferences.id")
@declared_attr
def question_tagging_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_tagging_preferences.id"))
@declared_attr
def question_tagging_preferences(cls):
return db.relationship("CustomTaggingPreferences", foreign_keys="custom_tagging_preferences.id")
@declared_attr
def answer_tagging_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_tagging_preferences.id"))
@declared_attr
def answer_tagging_preferences(cls):
return db.relationship("CustomTaggingPreferences", foreign_keys="custom_tagging_preferences.id")
@declared_attr
def comment_tagging_preferences_id(cls):
return db.Column(db.Integer, db.ForeignKey("custom_tagging_preferences.id"))
@declared_attr
def comment_tagging_preferences(cls):
return db.relationship("CustomTaggingPreferences", foreign_keys="custom_tagging_preferences.id")
对于那些面临与我的问题中描述的相同或类似问题的人：
通过将foreign_keys属性中的字符串变量替换为列变量本身，我成功地使代码正常工作。
经过测试，我发现使用字符串作为foreign_keys属性总是会触发错误，但使用primaryjoin和foreign_eys=cls.foreign_key的替代方法有效。
@declared_attr
def comment_event_preferences(cls):
return db.relationship("CustomEventPreferences", foreign_keys="custom_event_preferences.id")
变为：
@declared_attr
def comment_event_preferences(cls):
return db.relationship("CustomEventPreferences", foreign_keys=cls.comment_event_preferences)