Summary - Advanced classes
- TypeScript course
- Intermediate
- Lesson 65/89
- 4 min
Write a shape hierarchy with abstract class and interface.
Summary - Advanced classes
In this group you learned abstract classes, applying interfaces with implements, and getter/setter accessors. abstract class creates a base class; implements applies an interface contract to a class; get and set provide controlled access to properties.
abstract class Shape {
abstract area(): number;
}
class Square extends Shape implements Drawable {
get name() { return "square"; }
area() { return 4 * 4; }
draw() {}
}Practice Write the Sekil hierarchy
Define abstract class Sekil with abstract alan(): number. Define interface Cizilebilir with ciz(): void. Make Kare extend Sekil, implement Cizilebilir, take a kenar parameter, have alan return kenar * kenar, and ciz print "kare çizildi". In the last line print new Kare(3).alan().
Starter code
// Sekil adinda abstract sinif: alan metodu number donsun
// Cizilebilir adinda interface: ciz metodu void donsun
// Kare sinifi Sekil'i genişletip Cizilebilir'i uygulasin
// alan kenar*kenar donsun, ciz "kare çizildi" yazsin
// console.log(new Kare(3).alan());Sample solution
abstract class Sekil {
abstract alan(): number;
}
interface Cizilebilir {
ciz(): void;
}
class Kare extends Sekil implements Cizilebilir {
kenar: number;
constructor(kenar: number) { super(); this.kenar = kenar; }
alan(): number { return this.kenar * this.kenar; }
ciz(): void { console.log("kare çizildi"); }
}
console.log(new Kare(3).alan());Expected output
9
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 How to write a class that both inherits from a base class and implements an interface?
- class X abstract B implements I
- class X extends B, I
- class X extends B implements I Correct answer
- class X implements I extends B
Explanation: In TypeScript you write extends with the base class first, then implements with the interface; both can be in the same class.
2 Setter keyword
class Kasa {
private _para = 0;
____ para(v: number) { this._para = v; }
}class Kasa {
private _para = 0;
set para(v: number) { this._para = v; }
}Explanation: The accessor that runs when a value is assigned to a property is defined with the `set` keyword.
3 Advanced class concepts
| Term | Meaning |
|---|---|
abstract |
Base class marker |
implements |
Interface contract |
get |
Read accessor |
extends |
Inheritance |