TypeScript：应用于所有对象属性的分解函数

Question

假设我们有一些通用函数

function change<T>(something: T): IWhatever<T> {}

所以我可能有一个看起来像这样的对象

const stuff = {
    key1: change(1),
    key2: change('hello'),
    key3: change(false)
}

无论如何我可以制作一个看起来像这样的更简单的对象

const stuff = {
    key1: 1,
    key2: 'hello',
    key3: false
}

然后通过适当的 TypeScript 类型将更简单的对象传递给吐出第一个对象的函数？还假设更简单的对象可以随时更改属性，并且“某些功能”仍会产生适当的复杂对象。

我想不通，也不知道有没有可能。

Answer 1

好吧，您可以使用Mapped Types 来实现这一点。您只需要使用 2 种类型映射即可：

1. 剥离IWhatever<T>
2. 将剥离操作应用于每个属性

//  a weird interface
interface IWhatever<T> {
  whut: T;
}

// a weird function that wraps everything into that weird interface
function change<T>(something: T): IWhatever<T> { return { whut: something }; }


// general type that defines all properties has to be type of IWhatever<T>
type Whatevered<R> = {
  [key in keyof R]: IWhatever<R[key]>
}

// this object suits the type of we defined above
const stuff = {
  key1: change(1),
  key2: change('hello'),
  key3: change(false)
}

// this map strips the IWhatever type
type UnWhateverify<T> = T extends IWhatever<infer R> ? R : T;

// this applies strping to all properties of the object
type Cleanser<T> = { [Key in keyof T]: UnWhateverify<T[Key]> }

// this function is a dummy(magic) function that illustrates the type action
function MagicJhonson<R, T extends Whatevered<R>>(item: T): Cleanser<T> {
  let cleansed = {} as any;
  // doing the cleaning here
  for (let key in item)
    cleansed[key] = item[key].whut; // that general type definition `Whatevered<R>` makes this valid  
  // you can also skip that and do some cast to any action here.

  return cleansed as Cleanser<T>;
}

const cleansedStuff = MagicJhonson(stuff);

console.log(cleansedStuff.key1) // number
console.log(cleansedStuff.key2) // string
console.log(cleansedStuff.key3) // boolean


// another dummy function to reverse apply the operation
function JhonsonMagic<T>(item: T): Whatevered<T> {
  let whuts = {} as any;
  for (let key in item) {
    whuts[key] = change(item[key])
  }

  return whuts as Whatevered<T>;
}

const oldStuff = JhonsonMagic(cleansedStuff);

console.log(oldStuff.key1) // whut :number
console.log(oldStuff.key2) // whut :string
console.log(oldStuff.key3) // whut :boolean

Playground Link