Learn React with TypeScript 3

Implementing interfaces

We can use classes and interfaces together by defining the contract in an interface and then implementing the class as per the interface. We specify that a class is implementing a particular interface using the implements keyword.

As an example, we can define an interface for the order detail and then a class that implements this interface:

interface IOrderDetail {  product: Product;  quantity: number;  getTotal(discount: number): number;}class OrderDetail implements IOrderDetail {  product: Product;  quantity: number;  getTotal(discount: number): number {    const priceWithoutDiscount = this.product.unitPrice *       this.quantity;    const discountAmount = priceWithoutDiscount * discount; return priceWithoutDiscount - discountAmount; ...