Wrap typescript interface value types with some generic type

Question

Is there a way in Typescript to wrap all interface's values into some generic type to get another interface?

I have interface which represents an object with class constructors:

interface MyConstructors {
  foo: typeof Foo;
  bar: typeof Bar;
  // ... etc (many lines here)
}

Then I create instances of these classes:

const instances = {
  foo: new Foo(params),
  bar: new Bar(params)
};

Interface of that object should look like

interface MyInstances {
  foo: InstanceType<typeof Foo>;
  bar: InstanceType<typeof Bar>;
  // ... etc (many lines here)
}

As you can see it looks mostly the same as MyConstructors. So I'm looking for some way to avoid that duplication.

Lesiak · Accepted Answer · 2022-02-07 18:45:59Z

7

You can use a mapped type:

type MyInstanceType = {
  [key in keyof MyConstructors]: InstanceType<MyConstructors[key]>
}

// Same as:
// type MyInstanceType = {
//    foo: Foo;
//    bar: Bar;
//}

answered Feb 7, 2022 at 18:45

Lesiak

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