CODEWITHSUNDEEP
typescript
HardCoreQual
HardCoreQual

Reputation: 391

extends class declare properties using interface/type

I want declare some properties in class

class a extends legacyJsClass {
  declare id: number;
  declare name: string;
}

but also want that this properties can be reused in other places, but it isn't work

type I = {
  id: number;
  name: string;  
}

class a implements I {} // not work as declare
class a {
  declare [K in keyof I]: I[K]  // syntax don't exist
}

Thanks for any suggestion

Upvotes: 0

Views: 41

Answers (2)

HardCoreQual
HardCoreQual

Reputation: 391

After inspecting the example of captain-yossarian I write next solution

export type RawType = {
   name: string;
}

export interface Custom extends RawType {}

export class Custom extends Legacy<genericParam> {
  getName() {
    return this.name;
  }
}

Upvotes: 1

captain-yossarian from Ukraine
captain-yossarian from Ukraine

Reputation: 33091

You can use declaration merging.

Consider this example:

interface Shape {
  id: number;
  name: string;
}

class Shape { }

const foo = new Shape()
foo.id // number
foo.name // string

However, it is not super safe, because, as you may have noticed, there are no id and name properties in the class.

Hence, I think this approach is a bit safer:

interface Shape {
  id: number;
  name: string;
}

class Foo implements Shape {
  id = 42;
  name = 'John'
}

const foo = new Foo()
foo.id // number
foo.name // string

Upvotes: 1

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