CODEWITHSUNDEEP
typescript
Chad
Chad

Reputation: 493

TypeScript Index Signatures with Interface Types

I have an interface and a class:

interface Widget {
  widgetStuff(): void;
}

class Foo implements Widget {
  widgetStuff(): void {
  }
}

I want to track all of the Widgets in another class, and an index signature seems to be the easiest way:

class WidgetCatalog {
  private readonly mapping: { [key: string]: Widget };

  constructor() {
    this.mapping = {
      Foo // <= Error here
    }
  }
}

I'm getting this error: error TS2322: Type 'typeof Foo' is not assignable to type 'Widget'. Property 'widgetStuff' is missing in type 'typeof Foo'.

I'm not sure what Im missing here, since it seems to be a pretty straightforward implementation. Do I need to specify the value type in the index signature differently?

Upvotes: 0

Views: 118

Answers (1)

Chad
Chad

Reputation: 493

@jcalz pointed me in the right direction. This version works:

interface Widget {
  widgetStuff(): void;
}

class Foo implements Widget {
  widgetStuff(): void {
  }
}

class WidgetCatalog {
  // Change to mapping of Widget constructors
  private readonly mapping: { [key: string]: new(...args) => Widget };

  constructor() {
    this.mapping = {
      Foo
    }
  }
}

Upvotes: 1

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