Classes and Objects in TypeScript

Awesome! Let's now cover Classes and Objects in TypeScript, which are at the core of building services, components, and models in Angular.

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🔹 1. What is a Class?

A class is a blueprint for creating objects. It encapsulates data (properties) and behavior (methods).

✅ Basic Syntax

class Person {
  name: string;
  age: number;

  constructor(name: string, age: number) {
    this.name = name;
    this.age = age;
  }

  greet(): void {
    console.log(`Hello, my name is ${this.name}`);
  }
}
    

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🔹 2. Creating an Object

You can create objects (instances) from a class using the new keyword.

const person1 = new Person("Alice", 30);
person1.greet(); // Output: Hello, my name is Alice
    

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🔹 3. Access Modifiers

Modifier	Description
public	Accessible anywhere (default)
private	Accessible only within the class
protected	Accessible in the class & subclasses

class Employee {
  private salary: number;

  constructor(private name: string, salary: number) {
    this.salary = salary;
  }

  getSalary(): number {
    return this.salary;
  }
}
    

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🔹 4. Inheritance

Classes can extend other classes using extends.

class Manager extends Employee {
  department: string;

  constructor(name: string, salary: number, department: string) {
    super(name, salary);
    this.department = department;
  }

  display(): void {
    console.log(`${this.name} manages ${this.department}`);
  }
}
    

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🔹 5. Getter & Setter

Encapsulation using get and set methods:

class Product {
  private _price: number;

  constructor(price: number) {
    this._price = price;
  }

  get price(): number {
    return this._price;
  }

  set price(value: number) {
    if (value > 0) {
      this._price = value;
    }
  }
}
    

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🔹 6. Interfaces with Classes

A class can implement one or more interfaces.

interface Logger {
  log(message: string): void;
}

class ConsoleLogger implements Logger {
  log(message: string): void {
    console.log("Log:", message);
  }
}
    

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🧠 Summary

• Use classes to encapsulate logic and data.
• Create objects using new.
• Apply access modifiers to control visibility.
• Extend classes using inheritance.
• Use getters and setters for controlled access.
• Implement interfaces for structured behavior.

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