Hands-On Design Patterns with React Native

Structural typing

TypeScript uses structural typing. To understand what that means, let's look at the following example:

interface Donut {    flavour: FLAVOURS;}class ChocolateDonut {    flavour: FLAVOURS.CHOCOLATE;}let p: Donut;// OK, because of structural typingp = new ChocolateDonut();

In this example, we first declare the p variable, and then assign a new instance of ChocolateDonut to it. It works in TypeScript. It wouldn't work in Java. Why?

We have never explicitly indicated that ChocolateDonut implements the Donut interface. If TypeScript did not use structural typing, you would need to refactor part of the preceding code to the following:

class ChocolateDonut implements Donut {    flavour: FLAVOURS.CHOCOLATE;}

The reasoning behind using structural ...