How to Calculate the Total Cost of Products in a Cart using Eloquent Relationships?

Eloquent Sum of Relation's Column

One of the challenges when working with an e-commerce application is retrieving aggregated data from related models. In the context of a shopping cart, you might need to determine the total cost of products added to the cart.

Let's assume the following models:

• User: Represents a user with an 'id' and other attributes.
• Product: Represents a product with an 'id' and a 'price' attribute.
• Cart: Represents a shopping cart with an 'id', 'user_id', and 'product_id.'

Using Eloquent's relationships, we can establish that:

• A User hasMany Carts.
• A Cart belongsTo a User and hasMany Products.

To get the count of products in a user's cart, you can easily use:

Auth::user()->cart()->count();

However, calculating the total cost of products requires determining the sum of their prices. To do this with Eloquent without resorting to a raw query:

Auth::user()->products()->sum('price');

The 'products()' method retrieves all products associated with a user through the "belongsTo" and "hasMany" relationships, while the 'sum('price')' method aggregates the 'price' values from the products.

This Eloquent approach provides a clean and concise way to perform the desired operation, leveraging the power of its relationship management features.

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