Polymorphism through interfaces in Typescript - Mini Project: Build & Apply

Polymorphism through interfaces

📖 Scenario: You are building a simple system to handle different types of notifications in an app. Each notification type should be able to send its message in its own way.

🎯 Goal: Create an interface called Notifier with a method send(). Then create two classes EmailNotifier and SMSNotifier that implement this interface. Finally, use polymorphism to call send() on both types of notifiers.

📋 What You'll Learn

Create an interface called Notifier with a method send() that returns void.

Create a class called EmailNotifier that implements Notifier and its send() method prints 'Sending email notification'.

Create a class called SMSNotifier that implements Notifier and its send() method prints 'Sending SMS notification'.

Create an array called notifiers of type Notifier[] containing instances of EmailNotifier and SMSNotifier.

Use a for loop to call send() on each notifier in the notifiers array.

Print the output of each send() call.

💡 Why This Matters

🌍 Real World

Many apps send notifications in different ways like email, SMS, or push notifications. Using interfaces and polymorphism helps manage these different types easily.

💼 Career

Understanding polymorphism and interfaces is key for writing flexible and maintainable code in TypeScript and many other programming languages.

1

Create the Notifier interface

Create an interface called Notifier with a method send() that returns void.

Typescript

// Your code here

Need a hint?

An interface defines a contract. Here, Notifier must have a send() method that returns nothing.

2

Create EmailNotifier and SMSNotifier classes

Create a class called EmailNotifier that implements Notifier with a send() method that prints 'Sending email notification'. Also create a class called SMSNotifier that implements Notifier with a send() method that prints 'Sending SMS notification'.

Typescript

interface Notifier {
    send(): void;
}

// Your code here

Need a hint?

Use implements Notifier after the class name. The send() method should use console.log to print the messages.

3

Create an array of notifiers

Create an array called notifiers of type Notifier[] containing one instance of EmailNotifier and one instance of SMSNotifier.

Typescript

interface Notifier {
    send(): void;
}

class EmailNotifier implements Notifier {
    send(): void {
        console.log('Sending email notification');
    }
}

class SMSNotifier implements Notifier {
    send(): void {
        console.log('Sending SMS notification');
    }
}

// Your code here

Need a hint?

Create the array with the exact name notifiers and include one instance of each notifier class.

4

Call send() on each notifier and print output

Use a for loop with variable notifier to iterate over the notifiers array and call notifier.send() inside the loop.

Typescript

interface Notifier {
    send(): void;
}

class EmailNotifier implements Notifier {
    send(): void {
        console.log('Sending email notification');
    }
}

class SMSNotifier implements Notifier {
    send(): void {
        console.log('Sending SMS notification');
    }
}

const notifiers: Notifier[] = [new EmailNotifier(), new SMSNotifier()];

// Your code here

Need a hint?

Use a for...of loop to call send() on each notifier. The output should show both messages.