CODEWITHSUNDEEP
typescript
Mikael Lirbank
Mikael Lirbank

Reputation: 4615

TypeScript annotate inherited members of derived class

Say I have a base class and a number of derived classes. Is there a way to annotate the inherited members without having to re-implement them in the derived classes?

Consider something like this:

class BaseModel {
  collection: Collection;

  constructor(collectionName: string) {
    this.collection = connectToCollection(collectionName);
  }

  create(data: {}) { // <- I would like to annotate 'data' in the derived classes
    this.collection.insert(data);
  }
}

class ModelA extends BaseModel {
  constructor(collectionName: string) {
    super(collectionName);
  }
}

class ModelB extends BaseModel {
  constructor(collectionName: string) {
    super(collectionName);
  }
}

The argument for the create member is different for ModelA and ModelB, so I would like to annotate them separately.

I guess I can re-implement them like this:

class ModelA extends BaseModel {
  constructor(collectionName: string) {
    super(collectionName);
  }

  create(data: ArgsForModelA) {
    this.super.create(data);
  }
}

class ModelB extends BaseModel {
  constructor(collectionName: string) {
    super(collectionName);
  }

  create(data: ArgsForModelB) {
    this.super.create(data);
  }
}

But it just does not feel right, so I am curious to if it's possible to annotate the inherited members without re-implementing each one of them in all the derived classes (phew).

Upvotes: 0

Views: 168

Answers (1)

Tao
Tao

Reputation: 2242

You can use generics for this.

class BaseModel<T> {

  collection: Collection;

  constructor(collectionName: string) {
    this.collection = connectToCollection(collectionName);
  }

  create(data: T) {
    this.collection.insert(data);
  }
}

class ModelA extends BaseModel<ArgsForModelA> {
  constructor(collectionName: string) {
    super(collectionName);
  }
}

class ModelB extends BaseModel<ArgsForModelB> {
  constructor(collectionName: string) {
    super(collectionName);
  }
}

Upvotes: 3

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