TypeScript return object constructed form generic

Question

I\'d like to define following generic function to process conversion from interface type to class type implementing this interface. Consider following interface/class pair:

Answer 1

The problem is that O does not exist at runtime (generics are erased at runtime in typescript), and at runtime you need to use O to instantiate the new class. You need to pass the actual constructor to the function:

function fromInterfaceToObject<I, O extends I>(iIn: I, o: new (iIn: I) => O): O {
    return new o(iIn);
}

fromInterfaceToObject({ num: 10 }, Example);