Question

我正在编写一个程序来记录我的植物的过程和种子的种植日期。所有数据都可以通过REST-Api进行调整，但最后一次数据库迁移会让我感到厌烦。我想保存有关种植种子的数据（api.database.plantevent.py）：

class Plantevent(BaseTable):
"""
The database model for a planting event when seeds are planted.
"""
    __tablename__ = 'plantevents'

    plantdate = Column(Date, nullable=False)
    seed_id = Column(Integer, ForeignKey('seeds.id'), nullable=False)
    amount = Column(Integer, nullable=False)  # number of planted seeds
    sprouted = Column(Integer)  # number of sprouted seeds
    soaked = Column(Boolean)  
    first_seedling = Column(Date)  # Date of the first seedling
    plants = relationship("Plant", backref='plantevent')

＆＃34; BaseTable＆＃34;是一个抽象表，只包含id字段。

如果种子发芽，我想得到＆＃34; plantevent＆＃34;的所有植物。通过＆＃34;植物＆＃34;关系。这是工厂的模型（api.database.plant.py）：

class Plant(BaseTable):
"""
The database model for plants.
"""
    __tablename__ = 'plants'

    name = Column(String(255), nullable=False)
    crop_yield = Column(Integer)
    plantevent_id = Column(Integer, ForeignKey('plantevents.id'))

一切都很有效，除了＆＃34;植物＆＃34; - 关系＆＃34; Plantevent＆＃34;我无法弄清楚原因。如果我对＆＃34; plant＆＃34; -relationship发表评论，一切都会好的。为了完整性，这里是生成的sqlite-database的模式：

CREATE TABLE plantevents (
  id INTEGER NOT NULL, 
  plantdate DATE NOT NULL, 
  seed_id INTEGER NOT NULL, 
  amount INTEGER NOT NULL, 
  sprouted INTEGER, 
  soaked BOOLEAN, 
  first_seedling DATE, 
  PRIMARY KEY (id), 
  FOREIGN KEY(seed_id) REFERENCES seeds (id), 
  CHECK (soaked IN (0, 1))
);
CREATE TABLE plants (
  id INTEGER NOT NULL, 
  name VARCHAR(255) NOT NULL, 
  crop_yield INTEGER, 
  plantevent_id INTEGER, 
  PRIMARY KEY (id), 
  FOREIGN KEY(plantevent_id) REFERENCES plantevents (id)
);

我得到的错误，如果我尝试获得一个计划事件，请执行以下操作：

sqlalchemy.exc.InvalidRequestError: When initializing mapper Mapper|Plantevent|plantevents, expression 'Plant' failed to locate a name ("name 'Plant' is not defined"). If this is a class name, consider adding this relationship() to the <class 'api.database.plantevent.Plantevent'> class after both dependent classes have been defined.

有谁知道我为什么会收到此错误？我把它与db-model中的其他关系进行了比较，但我看不出有任何区别。

编辑：这是BaseTable的模型（api.database。 init .py）：

class BaseTable(Base):
    """
    Abstract base table which provides the id field for each table
    """
    __abstract__ = True

    id = Column(Integer, primary_key=True)

SQLAlchemy关系映射错误

0 个答案: