TypeScript constructor mass assignment

Question

I'm implementing Data Models for Database with TypeScript, and the code looks really ugly and verbose, is there any shorter version to declare it?

It's for MongoDB, so I would like to have an Interface for raw MongoDB document and the Model class separately. The ugly but working version looks like that

interface PostDocument {
  id:   number
  text: string
}

class Post implements PostDocument {
  id:   number
  text: string

  constructor(doc: PostDocument) {
    this.id = doc.id
    this.text = doc.text
  }
}

Ideally would be nice to have something like the code below, but I don't know if something like that possible with TypeScript

class Model<D> {
  somehow declare properties from D on Model
  constructor(document: D) { Object.assign(this, document)  }
}

interface PostDocument {
  id:   number
  text: string
}

class Post extends Model<PostDocument> {}

Alex Craft · Accepted Answer · 2019-02-22 09:48:59Z

1

Actually, it seems like it's possible

interface ModelConstructor<M, D> { new (document: D): M & D }

abstract class Model<D> {
  constructor(document: D) { Object.assign(this, document) }
}

function buildModel<D extends Object>(): ModelConstructor<Model<D>, D> {
  return Model as any
}

interface PostDocument {
  id:   number
  text: string
}

class Post extends buildModel<PostDocument>() {
}

const document: PostDocument = { id: 5, text: 'something' }
const post = new Post(document)
console.log(post.text)

answered Feb 22, 2019 at 9:48

Alex Craft

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