Summary - Access modifiers

Write a user class encapsulated with modifiers.

Summary - Access modifiers

A User class combines access modifiers: public name for everyone, private password fully hidden, protected role open to subclasses. Each field is declared with its own modifier and assigned with this in the constructor.

class User {
  public name: string;
  private password: string;
  protected role: string;
  constructor(name: string, password: string, role: string) {
    this.name = name;
    this.password = password;
    this.role = role;
  }
  checkPassword(pw: string): boolean {
    return this.password === pw;
  }
}
class Admin extends User {
  getRole(): string {
    return this.role;
  }
}

Exercise Write an encapsulated User class

Define a User class: explicitly declare public name: string and private password: string fields. Add a constructor that takes name and password parameters and assigns them with this. Write a checkPassword(pw: string): boolean method that returns this.password === pw. Create a new User("Ada", "s3cr3t"), call checkPassword("s3cr3t") and checkPassword("wrong").

Show example solution

class User {
  public name: string;
  private password: string;
  constructor(name: string, password: string) {
    this.name = name;
    this.password = password;
  }
  checkPassword(pw: string): boolean {
    return this.password === pw;
  }
}

const u = new User("Ada", "s3cr3t");
console.log(u.checkPassword("s3cr3t"));
console.log(u.checkPassword("wrong"));

Test yourself

Which modifier should the password field use in a User class?
- public
- protected
- static
- private
Show answer

private — Sensitive information like a password should be private; accessible only inside the class. public would be open to everyone, protected would be open to subclasses; both are unsafe.

Complete the password check

checkPassword(pw: string): boolean {
    return this.password ____ pw;
  }

Show answer

checkPassword(pw: string): boolean {
    return this.password === pw;
  }

Encapsulated User parts

public name

Public name for everyone
private password

Hidden password
protected role

Role open to subclass
extends User

Subclass definition

Next lesson: readonly fields

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