CODEWITHSUNDEEP
typescripttypescript-typings
Bruno Quaresma
Bruno Quaresma

Reputation: 10697

Typescript: How to define types for factory functions returning literal objects

I have the following function:

const ServerRequest = ({ token: ServerRequestOptions }) => ({
  async() {}
})

and I'm not able to use the ServerRequest as a directly type on my AuthService because it is a function so, I have to do some "tricks" like:

const AuthService = (request: ReturnType<typeof ServerRequest>) => ({ })

For me this trick does not sound good because to use a simple reference to the ServerRequest I have to compose some "complex" types. I also tried to export it as a diff type:

type ServerRequestType = ReturnType<typeof ServerRequest>

But I see many naming conventions saying to "never" use pre/postfix like I, Interface, Type, etc.

So, what should be the best path for this case?

Upvotes: 2

Views: 64

Answers (1)

Nenad
Nenad

Reputation: 26637

You just need type which defines function signature.

interface ServerRequestOptions {/* ...*/}

// Proper function signature
type ServerRequestFunc = (options: {token: ServerRequestOptions}) => void;

// variable holding function
const serverRequest: ServerRequestFunc = ({ token: ServerRequestOptions }) => ({
  async() {}
})

const authService = (request: ServerRequestFunc ) => ({ })

authService(serverRequest); // works fine.

Or even simpler,if we add name to our input parameter of serverRequest:

const serverRequest = (options: { token: string }) => ({
  async() {}
})

const authService = (request: typeof serverRequest) => ({ })

authService(serverRequest); // also works

Only, in 2nd example intellisense is not pretty (ex: hover over authService function in IDE).

Upvotes: 1

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