CODEWITHSUNDEEP
typescripttypescript-typings
Takeshi Tokugawa YD
Takeshi Tokugawa YD

Reputation: 923

How to access to interface or type alias which has not been explicitly exported in TypeScript type definitions?

I want to create the class inheretid from Vinyl. The constructor of superclass accepts the single parameter of ConstructorOptions type.

export default class MarkupVinylFile extends Vinyl {

  public constructor(options: ConstructorOptions) {
    super(options);
  }

  // ...

}

Currently I can't import the ConstructorOptions to use it as type annotation. In vinyl/index.d.ts is has been declared as:

interface ConstructorOptions {
    cwd?: string | undefined;
    // ...
}

It could not be imported as import Vinyl, { ConstructorOptions } from "vinyl";. Is it possible to import the ConstructorOptions?

📄 Vinyl Type Definitions

Upvotes: 1

Views: 272

Answers (1)

ghybs
ghybs

Reputation: 53225

As implied by @TobiasS. in the question comments, you can indirectly refer to this type.

Here we can use the ConstructorParameters built-in utility type for this purpose:

Constructs a tuple or array type from the types of a constructor function type.

// The vinyl types merge a variable, an interface and a namespace,
// so to get the "class", we have to tell TS to target the variable with `typeof`
type ConstructorOptions = ConstructorParameters<typeof Vinyl>[0];
//   ^? type ConstructorOptions = ConstructorOptions | undefined

// Alternatively, in case there are more than 1 argument,
// we could have used a rest operator with the full tuple:
export default class MarkupVinylFile extends Vinyl {

  public constructor(...args: ConstructorParameters<typeof Vinyl>) {
    super(...args);
  }

  // ...

}

Playground Link

That being said, if your constructor does nothing else than calling super(), you could just omit it.

Note: you should get an error when trying to extends Vinyl:

Base constructors must all have the same return type.(2510)

That is because the vinyl types declare several constructors with different return types.

Upvotes: 2

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