如何在SQLAlchemy中存储所选下拉值的ID

Question

我有两个类模型，它们转换为两个MySQL数据库表。一个是employees，另一个是projects。他们有一对多的关系，即一个项目可以有几个员工。在我的网络表单中注册员工时，我有一个包含项目的下拉列表。表employees，有一个引用projects表的外键，因此employees表有一个Integer列（emp_project_id）作为来自projects表的外键。从下拉列表中选择项目时如何保存ID？

class Employee(UserMixin, db.Model):
    """
    Create Employee table
    """

   # Ensures table will be named in plural and not in singular 
   # as in the name of the model
   __tablename__ = 'employees'

   id = db.Column(db.Integer, primary_key=True)
   emp_number = db.Column(db.String(10), index=True, unique=True, nullable=False)
   username = db.Column(db.String(60), index=True, unique=True)
   email = db.Column(db.String(60), index=True, unique=True, nullable=False)
   emp_name = db.Column(db.String(100), index=True)
   password_hash = db.Column(db.String(128))
   emp_project_id = db.Column(db.Integer, db.ForeignKey('projects.id'), nullable=False)

这是projects表

class Project(db.Model):
    """
    Create a Project table
    """

    __tablename__ = 'projects'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(60), unique=True, nullable=False)
    description = db.Column(db.String(200), nullable=False)

    pro_subprojects = db.relationship('Subproject', backref='sp_project', 
                                lazy='dynamic')
    pro_employees = db.relationship('Employee', backref='emp_project', 
                                lazy='dynamic')

如果可能的话，请将我推荐给我可以使用的资源，因为我没有在他们的文档中找到解决方案。

以下是forms.py创建表单的类

class RegistrationForm(FlaskForm):
    """
    Form for users to create new account
    """
    project = QuerySelectField(query_factory=lambda: Project.query.all(), 
                                                    get_label="name")
    subproject = QuerySelectField(query_factory=lambda: Subproject.query.all(), 
                                                    get_label="name")
    emp_number = StringField('Employee Number', validators=[DataRequired()])
    email = StringField('Email', validators=[DataRequired(), Email()])
    username = StringField('Username', validators=[DataRequired()])
    emp_name = StringField('Full Name', validators=[DataRequired()])
    password = PasswordField('Password', validators=[
                                            DataRequired(), 
                                            EqualTo('confirm_password')
                                        ])
    confirm_password = PasswordField('Confirm Password')
    submit = SubmitField('Register')

这是我在views.py上添加的内容：

@auth.route('/register', methods=['GET', 'POST'])
def register():
    """
    Handle requests to the /register route
    Add an employee to the database through the registration form
    """
    form = RegistrationForm()
    if form.validate_on_submit():
        employee = Employee(project=form.project.data,
                            subproject=form.subproject.data,
                            emp_number=form.emp_number.data,
                            email=form.email.data,
                            username=form.username.data,
                            emp_name=form.emp_name.data,
                            password=form.password.data)

        # add employee to the database
        db.session.add(employee)
        db.session.commit()
        flash('You have registered successfully. You can now log in.')

但是，当我尝试注册一名员工时，我收到了像TypeError: 'project' is an invalid keyword argument for Employee这样的错误。请帮助

Answer 1

这是the documentation for QuerySelectedField所说的内容：

data属性实际上将存储/保留ORM模型实例，而不是ID。

现在我明白你的问题改变了你的观点：

@auth.route('/register', methods=['GET', 'POST'])
def register():
    """
    Handle requests to the /register route
    Add an employee to the database through the registration form
    """
    form = RegistrationForm()
    if form.validate_on_submit():
        employee = Employee(
                            emp_number=form.emp_number.data,
                            email=form.email.data,
                            username=form.username.data,
                            emp_name=form.emp_name.data,
                            password=form.password.data)
        project=form.project.data  #an instance of Project Class
        subproject=form.subproject.data #an instance of SubProject Class
        project.pro_subproject.append(subproject) 
        project.pro_employee.append(employee)
        # add employee to the database
        db.session.add(employee)
        db.session.add(subproject)
        db.session.add(project)
        db.session.commit()
        flash('You have registered successfully. You can now log in.')

Here is an explanation of that :

一对多关系将外键放在引用父对象的子表上。然后在父项上指定relationship（），作为引用子项表示的项集合：

这意味着在项目表中，字段pro_employees和pro_subproject是employee（n）和sub_project（n）的列表。