打印出加入烧瓶的结果

Question

我正在制作一个 flask 应用程序，每个用户都可以在其中将他的员工添加到列表中。我有两个表：用户和员工，它们看起来像这样：

class User(UserMixin, db.Model):

    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(120), index=True, unique=True)
    password_hash = db.Column(db.String(128))
    emps = db.relationship('Employee', backref = 'boss', lazy = 'dynamic')


    def __repr__(self):
        return '<User {}'.format(self.username)

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password_hash, password)


class Employee(db.Model):

    __tablename__ = 'Employees'

    id = db.Column(db.Integer, primary_key=True)
    first_name = db.Column(db.String(64), index=True)
    last_name = db.Column(db.String(64), index=True)
    User_id = db.Column(db.Integer, db.ForeignKey(User.id))

    def __repr__(self):
        return '<Employee {0} {1}>'.format(self.first_name, self.last_name)

我尝试将此添加到我的用户 class 以便我可以加入这两个表：

    def user_employees(self):
        user_emps = User.query.join(Employee, User.id == Employee.User_id).filter(User.id == Employee.User_id)
        return user_emps

在我的 html 文件中我有这个：

{% block content %}

    {% for employee in employees %}
    <div>{{ employee }}</div>
    {% endfor %}

{% endblock %}

这是视图函数：

def Show_Employees():
    employees = current_user.user_employees()

    return render_template('emps.html', employees = employees)

但是这不起作用。我的页面上只写了这个：

<User test

预期的输出将是员工的名字和姓氏。我想问题出在连接上，但我无法弄清楚。有没有人遇到过类似的情况？

Answer 1

您无需担心手动加入，SQLalchemy 会为您处理所有这些。您可以通过 user.emps 访问用户员工，其中 returns 员工列表。我放弃了很多您的代码，您可以再次添加这些代码，只是为了让示例更小且易于理解。功能齐全：

from flask import Flask, render_template_string
from flask_sqlalchemy import SQLAlchemy
from flask_login import UserMixin

app = Flask(__name__)
db = SQLAlchemy(app)

class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    emps = db.relationship('Employee', backref = 'boss', lazy = 'dynamic')

class Employee(db.Model):
    __tablename__ = 'Employees'
    id = db.Column(db.Integer, primary_key=True)
    first_name = db.Column(db.String(64), index=True)
    User_id = db.Column(db.Integer, db.ForeignKey(User.id))

db.create_all() # creates the database tables, not needed if you already have them

boss1 = User()
boss1.username = 'Mr Boss'
employee1 = Employee()
employee1.first_name =  'Mr peanut'
employee2 = Employee()
employee2.first_name = 'Mr butter'
boss1.emps = [employee1, employee2] # here is where you're binding the employees to the user
db.session.add(boss1)
db.session.commit()

@app.route('/')
def index():
    user = User.query.get(1) # this returns the user with id1, which is 'Mr boss' 
    return render_template_string('''
    This is user {{user.username}}<br>
    His empoyees are:
    {% for employee in user.emps %} 
    <div>{{ employee.first_name }}</div>
    {% endfor %}
    ''', user=user)

app.run()

如果您访问该站点，将打印出：

This is user Mr Boss
His empoyees are:
Mr peanut
Mr butter

打印出加入烧瓶的结果

Printing out the results of a join in flask

python

flask

python-3.x

flask-sqlalchemy

flask-wtforms