How to make only specific methods in TypeScript class non-overridable (but still importable)? [duplicate]

Question

I'm using TypeScript and have a class that is exported so its methods can be imported and used elsewhere. However, I’d like to make only certain methods non-overridable when someone extends the class — not all of them.

For example:

export class BaseService {
  public doSomething(): void {
    console.log("Base logic");
  }

  public doSomethingImportant(): void {
    console.log("Critical logic that must not be overridden");
  }
}

I want the following to be allowed:

import { BaseService } from "./BaseService";

new BaseService().doSomethingImportant();

But I want TypeScript to forbid overriding only doSomethingImportant():

class MyService extends BaseService {
  public doSomethingImportant(): void {  // ❌ should cause a compile error
    console.log("Overridden critical logic");
  }
}

Is there any way to mark only some methods as final (non-overridable), while keeping the class and its methods importable and usable externally?

No, there is no final in TypeScript; there's an old request languishing at ms/TS#1534 but it's not part of the language. There are various workarounds. — jcalz
– jcalz, Commented Oct 13 at 12:19

Николай Гольцев · Accepted Answer · 2025-10-13 11:03:40Z

0

As a workaround you can use the following approach:

export class BaseService {
  public doSomething(): void {
    console.log("Base logic");
  }

  public doSomethingImportant(): void {
    console.log("Critical logic that must not be overridden");
  }
}

type NonOverridableBaseService = {
  doSomethingImportant?: never;
}

class MyService extends BaseService implements NonOverridableBaseService {
  public doSomethingImportant(): void {  // ❌ should cause a compile error
    console.log("Overridden critical logic");
  }
}

answered Oct 13 at 11:03

Николай Гольцев

1,3471 gold badge8 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

jcalz Oct 13 at 12:39

This causes a compile error even if you don't override doSomethingImportant.

Николай Гольцев Oct 13 at 12:50

You're right. Haven't checked this case. Seems, there is no opportunity to do it.

Collectives™ on Stack Overflow

How to make only specific methods in TypeScript class non-overridable (but still importable)? [duplicate]

1 Answer 1

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Linked

Related