Topic: connecting 2 products tables to one cart

hi

ive followed along the depot book. i have a products table, cart, line_items. All works fine there with adding the products to the cart etc.

now ive added another table user_products table. i want the user to be able to add these items to the cart also. but i dunno how to get this working. i tried to add in user_product code anywhere i saw code for the product table in the cart and line_item. also added that user_products belong to line_items too in the model like what is used for the products table.

i added an extra column in line_item table for user_product_id.

still cant get it working. any insight would be greatly appreciated need to get this fixed asap. can this be done..the cart taking in items from the products table and user_products table. Ive tried to find information on the web but to no avail..if anyone can point me to some info that would be great.