Chapter 10 — Class'lar

TypeScript — JavaScript class'lariga tip xavfsizligini, access modifikatorlarni va qo'shimcha OOP xususiyatlarini qo'shadi.

---

10.1 Asosiy Class Sintaksisi va Access Modifikatorlar

Example

index.ts
TypeScriptNusxalash
01class Person {
02  public name: string;       // hamma joydan kirish mumkin (standart)
03  private age: number;        // faqat shu class ichidan
04  protected email: string;    // shu class va uning avlodlaridan
05 
06  constructor(name: string, age: number, email: string) {
07    this.name = name;
08    this.age = age;
09    this.email = email;
10  }
11 
12  greet(): string {
13    return `Salom, men ${this.name}man`;
14  }
15}
16 
17const p = new Person("Abbosbek", 26, "a@example.com");
18console.log(p.name);   // TO'G'RI
19console.log(p.age);    // XATO: 'age' is private

10.2 Constructor Parameter Properties (Qisqartma Sintaksis)

Example

index.ts
TypeScriptNusxalash
01// Uzun usul
02class PersonLong {
03  name: string;
04  constructor(name: string) {
05    this.name = name;
06  }
07}
08 
09// Qisqartma — access modifikator bilan constructor parametrida
10class Person {
11  constructor(
12    public name: string,
13    private age: number,
14    readonly id: number
15  ) {}
16}
17 
18const p = new Person("Abbosbek", 26, 1);
19console.log(p.name); // "Abbosbek" — avtomatik xususiyat sifatida yaratildi

💡 Key Idea
Constructor parametriga to'g'ridan-to'g'ri access modifikator (public, private, protected, readonly) qo'yish — TypeScript'ga "bu parametrni avtomatik ravishda class xususiyatiga aylantir va thisga tayinla" deb aytadi, bu esa ko'p takrorlanadigan kodni yo'q qiladi.

10.3 Interfeys Implement Qilish va Abstract Class'lar

Example

index.ts
TypeScriptNusxalash
01interface Shape {
02  getArea(): number;
03}
04 
05class Circle implements Shape {
06  constructor(private radius: number) {}
07  getArea(): number {
08    return Math.PI * this.radius ** 2;
09  }
10}
11 
12abstract class Animal {
13  abstract makeSound(): void; // implementatsiyasiz, avlodlar berishi SHART
14 
15  move(): void {
16    console.log("Harakatlanmoqda...");
17  }
18}
19 
20class Dog extends Animal {
21  makeSound(): void {
22    console.log("Vov!");
23  }
24}
25 
26// const a = new Animal(); // XATO: Cannot create an instance of an abstract class

10.4 Static Xususiyatlar va Getter/Setter

Example

index.ts
TypeScriptNusxalash
01class Counter {
02  static count: number = 0;
03 
04  static increment(): void {
05    Counter.count++;
06  }
07 
08  private _value: number = 0;
09 
10  get value(): number {
11    return this._value;
12  }
13 
14  set value(newValue: number) {
15    if (newValue < 0) {
16      throw new Error("Manfiy qiymat bo'lishi mumkin emas");
17    }
18    this._value = newValue;
19  }
20}
21 
22Counter.increment();
23console.log(Counter.count); // 1 — instansiyasiz kirish mumkin
24 
25const c = new Counter();
26c.value = 10;      // setter chaqiriladi
27console.log(c.value); // getter chaqiriladi, 10

📝 Practice Exercises

🟢 Exercise 1 — Easy

Task: name (public) va balance (private) xususiyatlariga ega BankAccount class'ini yarating, parameter properties sintaksisidan foydalanib.

🟡 Exercise 2 — Medium

Task: Shape interfeysini implement qiluvchi Rectangle va Circle class'larini yarating, har biri o'z getArea() metodiga ega.

🔴 Exercise 3 — Hard

Task: validate() abstract metodiga ega abstract class Validator yaratib, undan EmailValidator va PhoneValidator class'larini hosil qiling.

🐛 Debugging Challenge

index.ts
TypeScriptNusxalash
01class Employee {
02  protected salary: number;
03  constructor(salary: number) {
04    this.salary = salary;
05  }
06}
07 
08class Manager extends Employee {
09  giveRaise(amount: number) {
10    this.salary += amount; // ?
11  }
12}
13 
14const emp = new Employee(5000);
15console.log(emp.salary); // ?

Your Task: Ikkita qatordan qaysi biri xato beradi?

<details> <summary>Solution</summary> Faqat `console.log(emp.salary);` xato beradi — `salary` `protected`, u faqat `Employee` class'ining O'ZIDAN yoki uning AVLODLARIDAN (masalan `Manager` ichida) kirish mumkin, lekin tashqaridan (masalan `emp.salary` orqali to'g'ridan-to'g'ri) kirish mumkin emas. `Manager` ichidagi `this.salary += amount;` esa to'g'ri ishlaydi, chunki `Manager` — `Employee`ning avlodi. </details>

📌 Chapter Summary

Class'lar — public/private/protected orqali kirish darajasini boshqaradi. Parameter properties — constructor kodini qisqartiradi. implements — interfeys kontraktini majburlaydi, abstract class — to'liq bo'lmagan shablon yaratadi. static — class darajasidagi a'zolar, getter/setter — nazoratli kirish/yozish imkonini beradi.

🎯 Key Takeaways

• public (standart), private, protected — kirish darajalarini boshqaradi
• Parameter properties — constructor(public x: T) — kodni qisqartiradi
• implements — interfeys, extends — meros uchun
• Abstract class — to'g'ridan-to'g'ri instansiya yaratib bo'lmaydigan, avlodlar to'ldirishi kerak bo'lgan shablon
• Getter/setter — xususiyatga kirish/yozishga qo'shimcha mantiq qo'shadi

⚡ Quick Cheat Sheet

index.ts
TypeScriptNusxalash
01class Person {
02  constructor(public name: string, private age: number) {}
03}
04interface Shape { getArea(): number; }
05class Circle implements Shape { getArea() { return 0; } }
06abstract class Base { abstract doWork(): void; }
07class Impl extends Base { doWork() {} }

---