类型缺少类型的以下属性？

Question

I got this message

Class 'Motorvoertuig' incorrectly implements interface 'Voertuig'.
Type 'Motorvoertuig' is missing the following properties from type 'Voertuig': toonMerk, wieIsDeEigenaar

But I really don't know why?

I have more code in this document but the error comes from the following Methodes.

interface Voertuig {
     merk: string;
    eigenaar: string;

    toonMerk(merk:string);
    wieIsDeEigenaar(eigenaar:string);
};
abstract class Motorvoertuig implements Voertuig {
  (Some code)
}

How to get rid of this error?

Answer 1

You have marked Motorvoertuig as implementing Voertuig interface that means you need to add all fields present in Voertuig interface to Motorvoertuig class. So for example:

abstract class Motorvoertuig implements Voertuig {
  merk: string = '';
  eigenaar: string = '';
  toonMerk(merk: string) {}
  wieIsDeEigenaar(eigenaar: string) {}
}

or you can try using something like:

abstract class Motorvoertuig implements Partial<Voertuig> {
}

check advanced typescript types

Answer 2

When you implement an interface, you need to define the properties that are declared in the interface. In Motorvoertuig , you probably have defined merk and eigenaar , but not toonMerk and wieIsDeEigenaar .

If you don't want to implement those methods inside your abstract class Motorvoertuig , you can make the methods abstract like this:

abstract toonMerk(merk: string);
abstract wieIsDeEigenaar(merk: string);