Summary - Advanced classes

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() {}
}

Exercise 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().

Show example 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());

Test yourself

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
- class X implements I extends B
Show answer

class X extends B implements I — In TypeScript you write extends with the base class first, then implements with the interface; both can be in the same class.

Setter keyword

class Kasa {
  private _para = 0;
  ____ para(v: number) { this._para = v; }
}

Show answer

class Kasa {
  private _para = 0;
  set para(v: number) { this._para = v; }
}

Advanced class concepts

abstract

Base class marker
implements

Interface contract
get

Read accessor
extends

Inheritance

Next lesson: as keyword

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