Mastering TypeScript Inheritance: Unlocking Code Reusability and Flexibility

Here’s a rewritten version of the article:

Unlocking the Power of Abstract Classes in TypeScript

When working with TypeScript, understanding abstract classes is crucial for creating robust and scalable code. But what exactly are abstract classes, and how do they differ from regular classes?

The Basics of Abstract Classes

In TypeScript, an abstract class is a blueprint that cannot be instantiated directly. Instead, it serves as a foundation for other classes to build upon. We declare an abstract class using the abstract keyword. For instance, consider a Shape class that cannot be created directly:

typescript
abstract class Shape {
//...
}


Abstract Methods: The Key to Flexibility

An abstract method is a function declared within an abstract class without a body. It ends with a semicolon (;) and must be implemented by any subclass. We use the same abstract keyword to create abstract methods. For example:

typescript
abstract class Shape {
abstract calculateArea(): number;
}


Notice how the calculateArea() method lacks a body and ends with a semicolon. If a class contains at least one abstract method, it must be declared abstract; otherwise, an error will occur.

Inheriting Behavior: Subclasses and Abstract Classes

A class that extends an abstract class is called a subclass (or child class). It inherits all non-abstract code and must implement all abstract methods. Let’s explore an example:

abstract class Shape {
  abstract calculateArea(): number;
}

class Square extends Shape {
  calculateArea(): number {
    return this.side * this.side;
  }
}

const square = new Square();
console.log(square.calculateArea()); // Output: area of the square

<p>In this example, the <code>Square</code> class extends the <code>Shape</code> abstract class and provides a concrete implementation of the <code>calculateArea()</code> method.</p>

<p><strong>Multiple Subclasses, One Abstract Class</strong></p>

<p>Abstract classes can have multiple subclasses, each implementing the abstract methods in their own way. Consider the following example:</p>

<p>“`typescript
abstract class Animal {
abstract sound(): void;
}

class Dog extends Animal {
sound(): void {
console.log(“Woof!”);
}
}

class Cat extends Animal {
sound(): void {
console.log(“Meow!”);
}
}

const dog = new Dog();
dog.sound(); // Output: Woof!

const cat = new Cat();
cat.sound(); // Output: Meow!
“`

Here, both Dog and Cat extend the Animal abstract class and implement the sound() method differently.

The Benefits of Abstract Classes

So, why do we use abstract classes in TypeScript? There are several compelling reasons:

• Define a common structure: Abstract classes help define a shared structure for related classes.
• Ensure implementation: By using abstract methods, we can guarantee that all child classes implement specific methods.
• Share code, customize behavior: Abstract classes allow us to write shared code for all child classes while letting them define their own specific parts.

By mastering abstract classes, you’ll be able to create more robust, scalable, and maintainable code in TypeScript.