Question

我无法从子类访问父类成员变量@Override protected void configure(HttpSecurity http) throws Exception { http. authorizeRequests() .antMatchers("/").permitAll() .antMatchers("/index").permitAll() .antMatchers("/login").permitAll() .antMatchers("/confirmarRegistro").permitAll() .antMatchers("/registration").permitAll() .antMatchers("/admin/**").hasAuthority("ADMIN") .antMatchers("/titular/**").hasAuthority("TITULAR") .antMatchers("/sgc/**").hasAuthority("SGC") .antMatchers("/usuario/**").hasAuthority("USUARIO").anyRequest() .authenticated().and().csrf().disable().formLogin() .loginPage("/index").failureUrl("/login?error=true") .successHandler(successHandler) .usernameParameter("email") .passwordParameter("password") .and().logout() .logoutRequestMatcher(new AntPathRequestMatcher("/logout")) .logoutSuccessUrl("/").and().exceptionHandling() .accessDeniedPage("/access-denied"); }。

id

给我这个错误：

class BaseModel:
    id = db.Column(db.Integer, primary_key=True)

class User(db.Model, BaseModel):
    username = db.Column(db.String(35), nullable=False, unique=True)

    followed = db.relationship(
        'User',
        secondary=followers,
        primaryjoin=(followers.c.follower_id == BaseModel.id),
        secondaryjoin=(followers.c.followed_id == BaseModel.id),
        backref=db.backref('followers', lazy='dynamic'),
        lazy='dynamic')

另一方面

sqlalchemy.exc.InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers. Triggering mapper: 'Mapper|User|user'. Original exception was: Could not locate any simple equality expressions involving locally mapped foreign key columns for primary join condition 'followers.follower_id = "<name unknown>"' on relationship User.followed.  Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or are annotated in the join condition with the foreign() annotation. To allow comparison operators other than '==', the relationship can be marked as viewonly=True.

给我这个错误：

class BaseModel:
    id = db.Column(db.Integer, primary_key=True)

class User(db.Model, BaseModel):
    username = db.Column(db.String(35), nullable=False, unique=True)

    testing = BaseModel.id

Answer 1

类定义的主体是它自己的范围，引入的名称将构成类的命名空间。模型定义的问题（在您的original question中）是在类id的主体中尚未分配名称User，因此在{{1}中加入了}定义是指内置函数id()。您也不能使用此问题中所示的relationship，因为Declarative元类将create a copy of it to User，因此它不会引用同一列。

解决方案是使用惰性求值：将可调用或Python可求值的字符串作为连接传递：

BaseModel.id

之所以可行，是因为除非声明了configure_mappers()明确配置，否则映射器的映射器间关系是在声明了映射的类之后配置的，并且是第一次使用。

请注意，您也不能在可评估字符串中使用普通的followed = db.relationship( 'User', secondary=followers, primaryjoin='followers.c.follower_id == User.id', # Note: the joins are secondaryjoin='followers.c.followed_id == User.id', # passed as strings backref=db.backref('followers', lazy='dynamic'), lazy='dynamic')，而必须使用id类来引用它，因为稍后对其进行评估的范围与该类的范围完全不同正文including names from the Declarative class registry, and metadata。

最后一个错误是诸如

之类的代码的结果

User

在类主体中将User.query.get(some_id)分配给另一个名称（例如BaseModel.id）会导致您的模型具有由2个整数列组成的复合主键，因此预期Query.get()接收2个元组的整数，而不仅仅是一个整数。

从子级访问mixin成员变量（列）

1 个答案: