How to infer type from interface part with nested structure?

Question

typescript

Let's say I have an interface like this:

interface Book {
    id: number,
    author: {
        name: string,
        age: number,
    },
    price: {
        value: number,
        currency: Currency,
    }
}

I want to make a function that will only work with the author field from this interface. Those. the function should expect an object of this type:

function doSomething(author: {name: string, age: number})

How can I automatically infer the type from the Book interface? I tried to do , but as a result I get , but I just need . {name: string, age: number}Pick<Book, "author">{author: {name: string, age: number}}{name: string, age: number}

Answer 1

Book['author']
But if you need different parts of the interface to walk around the program, then it is better to break it into pieces

interface BookAuthor { ... }
interface BookPrice { ... }
interface Book {
  id: number,
  author: BookAuthor,
  price: BookPrice
}