models.py

# from flaskblog folder in __init__.py
from enum import unique
from datetime import datetime
from app import db
from sqlalchemy import Column, Integer, String
from flask_login import UserMixin
from flask_login import LoginManager

# https://stackoverflow.com/questions/63231163/what-is-the-usermixin-in-flask

# one to many relationship between both databases

class User(UserMixin, db.Model):
    # The primary key creates the one in an one to many relationship between both databases
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    hashed_password = db.Column(db.String(128), nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    # backref='user' connects to the user database. You name the backref= the same name as the database - the capital letter
    # Connects Post database and User database through the posts variable
    posts = db.relationship('Posts', backref='user', lazy=True)
    # what does this do?
    def __repr__(self):
        return '<User %r>' % self.username


class Posts(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(120), unique=True, nullable=False)
    content = db.Column(db.String(120), unique=True, nullable=False)
    date_posted = db.Column(db.DateTime, nullable=False,
        default=datetime.utcnow)
    # The foreign key creates the many in an one to many relationship between both databases
    # user.id represents the id from the User database and the posts variable specifically backref='user'
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
    # what does this do?
    def __repr__(self):
        return '<Posts %r>' % self.username


from app import login_manager
# Use User.query.get instead of User.get because of sqlalchemy
# what is user_id
@login_manager.user_loader
def load_user(user_id):
   return User.query.get(user_id)