Flask Tutorials: User Model and Loader 🎯

Welcome to this comprehensive guide on creating a User Model and Loader using Flask! This tutorial is designed to be friendly and approachable, so let's get started.

Understanding the User Model 📝

A User Model is a representation of a user in a database. It's crucial for managing user data, such as username, email, password, and other personal details.

python

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    password = db.Column(db.String(128))

    def __repr__(self):
        return f"<User {self.username}>"

💡 Pro Tip: Flask provides flask_sqlalchemy for easy database integration.

Creating the User Loader 💡

The User Loader is responsible for fetching user data from the database by their ID.

python

from werkzeug.security import check_password_hash, generate_password_hash

def get_user_by_id(user_id):
    user = User.query.get(user_id)
    return user

def set_password(user, password):
    user.password = generate_password_hash(password)

def check_password(user, password):
    return check_password_hash(user.password, password)

📝 Note: Always hash the password before storing it in the database for security reasons.

Practical Application 🎯

Let's create a simple registration and login function using our User Model and Loader.

python

@app.route('/register', methods=['GET', 'POST'])
def register():
    if request.method == 'POST':
        username = request.form['username']
        email = request.form['email']
        password = request.form['password']

        user = User(username=username, email=email, password=password)
        db.session.add(user)
        db.session.commit()

        return redirect(url_for('login'))

    return render_template('register.html')

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        email = request.form['email']
        password = request.form['password']

        user = get_user_by_id(1)  # In a real app, fetch user by email
        if check_password(user, password):
            # If login successful, do something like redirect to user's dashboard
            return redirect(url_for('dashboard'))

        # If login fails, show an error message
        return render_template('login.html', error="Invalid credentials.")

    return render_template('login.html')

Quiz 💡

That's it for this lesson! In the next tutorial, we'll delve deeper into Flask, exploring topics like User Authentication and Authorization. Happy coding! 🎉🍻