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抽象方法必須在抽象類里 抽象父類中的抽象方法必須在子類中實現(xiàn) 抽象類不能被實例化
function makeArea(shape: Shape) {
return shape.getArea()
}
abstract class Shape {
abstract getArea(): number
}
class Rectangle extends Shape {
private width: number
private height: number
constructor(width: number, height: number) {
super()
this.width = width
this.height = height
}
getArea() {
return this.width * this.height
}
}
class Circle extends Shape {
private r: number
constructor(r: number) {
super()
this.r = r
}
getArea() {
return this.r * this.r * 3.14
}
}
const rectangle = new Rectangle(20, 30)
const circle = new Circle(10)
console.log(makeArea(rectangle))
console.log(makeArea(circle))
// makeArea(new Shape())
// makeArea(123)
// makeArea("123")
