How to convert custom interface to Record?

Question

Given the following sample code

interface MyInterface { foo: string; }

function doSomethingWith(x: Record<string, unknown>) { /* ... */ }

const myInterface: MyInterface = { foo: 'bar' };

doSomethingWith(myInterface);

It is not possible to pass the variable to the function because

Argument of type 'MyInterface' is not assignable to parameter of type 'Record<string, unknown>'. Index signature for type 'string' is missing in type 'MyInterface'.(2345)

I solved the problem by converting the variable

const myInterfaceAsRecord = (myInterface as unknown) as Record<string, unknown>;

and would like to know if there are any "better" ways to pass in the interface to the function?

Answer 1

Just use type instead interface

type MyInterface = { foo: string; }

function doSomethingWith(x: Record<string, unknown>) { /* ... */ }

const myInterface: MyInterface = { foo: 'bar' };

doSomethingWith(myInterface);

See this answer for more context

Answer 2

One option would be to extend the interface from the record:

interface MyInterface extends Record<string, unknown> { foo: string; }

function doSomethingWith(x: Record<string, unknown>) { /* ... */ }

const myInterface: MyInterface = { foo: 'bar' };

doSomethingWith(myInterface);