Obtain the specific generic type that is employed to broaden the scope of a

Question

I am working on a class that involves generics:

abstract class Base<P extends SomeType = SomeType> {
  // ...
}

In addition, there is a subclass that inherits from it:

class A extends Base<SomeTypeA> {
  // ...
}

I'm trying to figure out if TypeScript supports a way to determine "What type did class A use when extending Base?"

Essentially, I want something like

type PropType = ExtendedGeneric<A> // SomeTypeA

Answer 1

Answer №1

To extract the type passed to Base, you can utilize a conditional type.

type ExtendedGeneric<T extends Base<any>> = T extends Base<infer P> ? P: never
type PropType = ExtendedGeneric<A> // SomeTypeA

For further information on conditional types, refer to this resource

Answer 2

To extract the type passed to Base, you can utilize a conditional type.

type ExtendedGeneric<T extends Base<any>> = T extends Base<infer P> ? P: never
type PropType = ExtendedGeneric<A> // SomeTypeA

For further information on conditional types, refer to this resource

Answer 3

To integrate this function into your foundational code, simply follow these steps:

abstract getStructure(): Constructible<Format>;

You will also need to create a Constructible interface:

export interface Constructible<S> {
    new (data): S;
}

Afterwards, within your A class, include the following implementation:

class A extends Core<SomeTypeA> {
  getStructure(): Constructible<SomeTypeA> {
    return SomeTypeA;
  }
  // ...
}

Answer 4

To integrate this function into your foundational code, simply follow these steps:

abstract getStructure(): Constructible<Format>;

You will also need to create a Constructible interface:

export interface Constructible<S> {
    new (data): S;
}

Afterwards, within your A class, include the following implementation:

class A extends Core<SomeTypeA> {
  getStructure(): Constructible<SomeTypeA> {
    return SomeTypeA;
  }
  // ...
}