Challenge 1: Classes
- TypeScript course
- Intermediate
- Lesson 86/89
- 6 min
Solve a task combining classes and access modifiers.
Classes challenge
In this challenge you will solve tasks that combine classes, access modifiers (public, private, protected) and readonly fields. You learned to keep a class's internal state hidden while providing controlled access through accessor methods, and to build inheritance hierarchies with abstract classes. Now it is time to combine this knowledge.
Practice Write a Bank class
Define a Banka class with a private _bakiye: number field. The constructor takes baslangic: number and assigns _bakiye. get bakiye(): number returns the value. set bakiye(v: number) sets to 0 if negative. yatir(m: number): void adds m to _bakiye. Create new Banka(100), deposit 50, print bakiye.
Starter code
// Banka sinifi tanimla
// bakiye alani gizli olsun
// bakiye icin erisimci yaz
// para yatirma metodu ekle
// sonucu yazdirSample solution
class Banka {
private _bakiye: number;
constructor(baslangic: number) { this._bakiye = baslangic; }
get bakiye(): number { return this._bakiye; }
set bakiye(v: number) { if (v < 0) this._bakiye = 0; else this._bakiye = v; }
yatir(m: number): void { this._bakiye += m; }
}
const b = new Banka(100);
b.yatir(50);
console.log(b.bakiye);Expected output
150
Practice Shape hierarchy
Define abstract class Sekil with a protected renk: string field and constructor taking renk. Declare abstract alan(): number. goster(): void should print this.renk with console.log. Daire extends Sekil, takes private yaricap: number, constructor calls super(renk), alan() returns 3 * yaricap * yaricap. Create new Daire("kirmizi", 2) and call goster().
Starter code
// Sekil adinda abstract sinif
// renk alani korumali olsun
// alan metodu abstract olsun
// goster metodu rengi yazdirsin
// Daire Sekilden turetilsin
// alan metodunu uygula
// goster cagirSample solution
abstract class Sekil {
protected renk: string;
constructor(renk: string) { this.renk = renk; }
abstract alan(): number;
goster(): void { console.log(this.renk); }
}
class Daire extends Sekil {
private yaricap: number;
constructor(renk: string, yaricap: number) {
super(renk);
this.yaricap = yaricap;
}
alan(): number { return 3 * this.yaricap * this.yaricap; }
}
const d = new Daire("kirmizi", 2);
d.goster();Expected output
kirmizi
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which access modifier allows access only from within the class and its subclasses?
- private
- readonly
- protected Correct answer
- public
Explanation: protected members are accessible only within the class where they are defined and its subclasses; not from outside.
2 Protected access modifier
class Ust {
____ _gizli: string;
constructor(g: string) { this._gizli = g; }
}
class Alt extends Ust {
goster() { return this._gizli; }
}class Ust {
protected _gizli: string;
constructor(g: string) { this._gizli = g; }
}
class Alt extends Ust {
goster() { return this._gizli; }
}Explanation: The field must be protected so the subclass can also access it; if it were private, the subclass could not.
3 Access modifiers
| Term | Meaning |
|---|---|
private |
Only within the class |
protected |
Class and subclasses |
public |
From anywhere |
readonly |
Read-only |