How to get optional opts type signature to compile - TS2394

Question

I have this method, with 2 possibilities:

  requestLockInfo(key: string, cb: EVCb<any>): void;
  requestLockInfo(key: string, opts: any, cb: EVCb<any>): void;
  requestLockInfo(key: string, opts: any, cb: EVCb<any>) {
      // implementation
  }

the problem is it won't compile, it says:

Does anyone know how to create an optional options object in the signature like this? I have this problem a lot, and making the last argument optional with cb? doesn't usually solve the root problem.

lukasgeiter · Answer 1 · 2019-08-31T20:38:54.667

The implementation signature needs to basically be the result of merging the two other signatures. In this case that means:

requestLockInfo(key: string, cb: EVCb<any>): void;
requestLockInfo(key: string, opts: any, cb: EVCb<any>): void;
requestLockInfo(key: string, opts: any | EVCb<any>, cb?: EVCb<any>) {
    // implementation
}

The second argument opts can be either any (in case of the signature with 3 arguments) or EVCb<any> (in case of the signature with 2 arguments).

The third argument cb needs to be optional because in case of the signature with 2 arguments, it is not defined.

How to get optional opts type signature to compile - TS2394

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