Element Interface (IShoppingCartElement):?

Short answer: The IShoppingCartElement interface declares the Accept method, which allows the element to accept a visitor. Each element (like Book, Fruit) will implement this interface to allow a visitor to operate on it.

Example code

public interface IShoppingCartElement
{ void Accept(IShoppingCartVisitor visitor); }

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.