Access Modifiers

1. Welcome and Icebreaker:

• If you could make any part of your life private, protected, or public, what would you choose and why?

2. Outline the Session:

• We’ll learn about access modifiers in TypeScript: public, private, and protected.
• Learning Outcomes: Understand how to control access to class members and why encapsulation is important.
• Let’s see how to protect our data!

3. Concept Explanation:

• Access Modifiers control the visibility of class properties and methods.
• public: Accessible from anywhere (default).
• private: Accessible only within the class.
• protected: Accessible within the class and its subclasses.
• Encapsulation helps prevent unintended access or modification of data.

4. Live Coding Demonstration:

class User {
  public username: string;
  private password: string;
  protected email: string;

  constructor(username: string, password: string, email: string) {
    this.username = username;
    this.password = password;
    this.email = email;
  }

  public greet() {
    console.log(`Hello, ${this.username}!`);
  }

  private resetPassword() {
    console.log("Password reset!");
  }

  protected sendEmail() {
    console.log(`Email sent to ${this.email}`);
  }
}

const user = new User("alice", "secret", "alice@example.com");
user.greet(); // OK
// user.password; // Error: private
// user.resetPassword(); // Error: private
// user.sendEmail(); // Error: protected

class Admin extends User {
  promote() {
    // this.password; // Error: private
    this.sendEmail(); // OK: protected
  }
}

5. Tasks:

• Short Exercise:
  1. Create a class Account with properties: owner (public), balance (private), and accountNumber (protected).
  2. Add a method to deposit money (public) and a method to get the balance (public).
  3. Try to access balance and accountNumber from outside the class and from a subclass.