I got this error when I run my code.
"sqlalchemy.exc.NoForeignKeysError: Could not determine join condition between parent/child tables on relationship TopCities.posts - there are no foreign keys linking these tables. Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression."
Here is my code:
models.py
from app import db
from datetime import datetime
class TopCities(db.Model):
id = db.Column(db.Integer, primary_key=True)
city_name= db.Column(db.String(64), unique=True, index=True)
city_rank = db.Column(db.Integer())
posts = db.relationship('Post', backref='author', lazy='dynamic')
def __repr__(self):
return f'{self.city_name} with rank {self.city_rank}'
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
body = db.Column(db.String(256))
timestamp = db.Column(db.DateTime, default=datetime.utcnow)
user_id = db.Column(db.Integer, db.ForeignKey('TopCities.id'))
def __repr__(self):
return f'<Post> {self.id}: {self.body}>'
routes.py
from app import app_obj
from app.forms import TopCities
from flask import render_template, flash, redirect
from app import db
from app.models import TopCities, Post
@app_obj.route("/login", methods = ['GET','POST'])
def login():
name = 'Khuong'
title = 'Top Cities'
top_cities = TopCities.query.all()
form = TopCities()
if form.validate_on_submit():
top_cities = Topcities.query.all(city_name=form.city_name.data)
if top_cities is None or not top_cities.check_city_rank(form.city_rank.data):
flask('Invalid city_name or city_rank')
else:
top_cities = TopCities(city_name = form.city_name.data, city_rank = form.city_rank.data)
db.sesion.add(top_cities)
db.session.commit()
flask('New city is added!')
return redirect('/')
return render_template("home.html", name=name, title=title, form=form)
__init__.py
import flask
import os
from flask_sqlalchemy import SQLAlchemy
basedir = os.path.abspath(os.path.dirname(__file__))
#instance of the flask class
app_obj = flask.Flask(__name__)
app_obj.config.from_mapping(
SECRET_KEY = 'it-dont-matter',
SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(basedir, 'app.db'),
SQLALCHEMY_TRACK_MODIFICATIONS = False
)
db = SQLAlchemy(app_obj)
from app import routes, models
forms.py
from flask_wtf import FlaskForm
from wtforms import StringField, IntegerField, BooleanField, SubmitField
from wtforms.validators import DataRequired
class TopCities(FlaskForm):
city_name = StringField('City Name',validators=[DataRequired()])
city_rank = IntegerField('City Rank',validators=[DataRequired()])
is_visited = BooleanField('Visited')
submit = SubmitField('Submit')
base.html
<!DOCTYPE html>
<html>
<head>
{% if title %}
<title>{{title}}!</title>
{% else %}
<title>Home</title>
{% endif %}
</head>
<body>
{% with messages = get_flashed_messages() %}
{% if messages %}
<ul>
{% for m in message %}
<li>{{ m }}</li>
{% endfor %}
</ul>
{% endif %}
{% endwith %}
{% block content %}
{% endblock %}
</body>
</html>
home.html
{% extends "base.html" %}
{% block content %}
<h1> Welcomee {{name}}, here are top destinations! </h1>
<a href="https://www.google.com">goooogle</a>
<ul>
{% for city in top_cities %}
<li>{{ city }}</li>
{% endfor %}
</ul>
<form method="POST" novalidate>
{{ form.hidden_tag() }}
<p> {{ form.city_name.label }} <br>
{{ form.city_name(size=40) }}</p>
<p> {{ form.city_rank.label }} <br>
{{ form.city_rank(size=40) }}</p>
<p> {{ form.is_visited.label }} <br>
{{ form.is_visited() }}</p>
<p> {{ 'Submit' + form.submit() }}</p>
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