Realization

Realization is also a type of inheritance but for interfaces. In a realization relationship, one entity (normally an interface) defines a set of functionalities as a contract and the other entity (normally a class) realizes the contract by implementing the functionality defined in the contract.

For example, a car is Drivable (people can drive it), so it should have a drive() function. Let's look at a coded example:

1// Drivable.js
2class Drivable {
3    drive() {
4        throw new Error("You have to implement the method drive!")
5    }
6}
7
8// Car.js
9class Car extends Drivable {
10    // Must implement all functions of Drivable
11    drive() {
12        // Do the driving here
13    }
14}

This code can be presented in UML by the following picture.