cannot change list attribute of current_user in flask

Question

I want to create a cart for my website. Here is my User class:

class User(UserMixin, db.Model):
    __tablename__ = 'users'
    user_id = db.Column(db.Text, primary_key=True)
    password = db.Column(db.Text)
    roles = db.Column(db.String(length=25))
    stall_id = db.Column(db.Integer, db.ForeignKey('stalls.stall_id'), nullable=True)
    cart = []

    def __init__(self, user_id, password, role):
        self.user_id = user_id
        self.password = password
        self.roles = role

    def get_id(self):
        return self.user_id

The user can add items to the cart, I am using UserMixin and current_user to access the cart of the user. Everything works fine here.

@app.route('/add-to-cart/<int:picked_dish_id>', methods=['GET', 'POST'])
@login_required
def add_to_cart(picked_dish_id):
    dish = Dish.query.filter_by(dish_id=picked_dish_id).first()
    current_user.cart.append(dish)
    print(current_user.cart)
    return render_template('add_to_cart.html', dish=dish)

But I have problems with deleting the item from the cart, here is my function

@app.route('/delete-from-cart/<int:dish_id>')
@login_required
def delete_from_cart(dish_id):
    print(current_user.cart)
    dishes = current_user.cart
    current_user.cart = [dish for dish in dishes if dish.dish_id != int(dish_id)]
    print("Cart after deleting ", end='')
    print(current_user.cart)
    return redirect(url_for('checkout'))

After this function is called I am rendering the checkout page again to update the changes

@app.route('/checkout')
@login_required
def checkout():
    print("Cart in checkout: ", end='')
    print(current_user.cart)
    return render_template('checkout.html', cart=current_user.cart)

So when I am pressing delete button in my front-end firstly delete_from_cart function and after that it redirects user to checkout page to update the changes.

So here is the output of this two functions when I am trying to delete the item from the cart

[<Dish 1>, <Dish 4>]
Cart after deleting [<Dish 4>]
Cart in checkout: [<Dish 1>, <Dish 4>]

As you can see the function actually deletes the item from the cart and in function delete_from_cart current_user.cart list is different, but when it redirects to the checkout page the changes disappear.

Asked By: MisteryDush

||

Source

Answer 1

I dont know but .remove() function works completely fine and now I can remove items from the cart now

@app.route('/delete-from-cart/<int:dish_id>', methods=['POST'])
@login_required
def delete_from_cart(dish_id):
    for dish in current_user.cart:
        if dish.dish_id == dish_id:
            current_dish = dish
    current_user.cart.remove(current_dish)
    return redirect(url_for('checkout'))

Answered By: MisteryDush

cannot change list attribute of current_user in flask

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