Saving the category of a generic within an interface in TypeScript

I am working with a simple interface that looks like this:

interface A<T extends Object> {
  b: T;
}

Currently, "b" is stored as an instance of T. However, I want to store the non-instanced version of T as a value within the interface.

My initial idea was to try something like this:

interface A<T extends Object> {
  b: typeof T;
}

Unfortunately, it seems like this approach is not correct and is not allowed by the compiler. Is there a way to achieve what I want?

The following code accomplishes my goal, but it does not enforce 'b' to be generic:

interface A<T extends Object> {
  b: Object;
}

Answer №1

If you want to reference the type of a class constructor, you can utilize what is known as a construct signature. Here’s how it is structured:

interface A<T extends object> {
    instance: T; 
    ctor: new (...args: any) => T; 
}

Here is an illustration demonstrating its usage:

const aDate: A<Date> = {
    instance: new Date(),
    ctor: Date
} // This is acceptable

Try out the code on the playground

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