在 TypeScript 中递归展开对象类型

Question

I want to unwrap some types in TypeScript, here is example:

    // previously defined Type<T>

    // example of wrapped type:
    type Wrapped = Type<{
      a: Type<boolean>,
      b: Type<{
        c: Type<number>
      }>
    }>

    type Unwrap = ...// this needs to be defined

    //And its usage like:
    type Unwrapped1 = Unwrap<Wrapped>// should be: { a: boolean, b: { c: number } }
    type Unwrapped2 = Unwrap<Type<string>>// should be: string
    .
    .
    .

How Unwrap can be defined?

Answer 1

You can use mapped and conditional types and mapped types to unwrap the type:

type UnwrapObject<T> = {
  [P in keyof T] : Unwrap<T[P]>
}
type Unwrap<T> =  T extends Type<infer U> ? 
  U extends object ? UnwrapObject<U> : U: 
  T extends object ? UnwrapObject<T> : T

//And its usage like:
type Unwrapped1 = Unwrap<Wrapped>// should be: { a: boolean, b: { c: number } }
type Unwrapped2 = Unwrap<Type<string>>// should be: string

declare let d: Unwrapped1;
d.b.c // number

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