1

Hello i am trying to add correct type to object with nested values.

Here is code in sandbox: https://codesandbox.io/s/0tftsf

interface Product {
  name: string,
  id: number
  productList?:ProductItem[]
}

interface ProductItem { 
  color: string, 
  size: number 
 }


type IValidation<T> = {
  field: keyof T
  nestedValidations?: IValidation<
    Pick<
      T,
      {
        [K in keyof T]-?: T[K] extends object ? K : never
      }[keyof T]
      >
    >[] // THIS IS IMPORTANT FOR QUESTION!
  validators?: (any | any | any)[]
}

export async function validateIt<T>(payload: T, validations: IValidation<T>[]): Promise<
  Partial<{
    [key in keyof T]: string[]
  }>
  > { 
    return Promise.resolve(payload);
  }

const product: Product = {
  id: 1,
  name: 'playstation',
  productList: [{
    color: 'red',
    size: 32
    }
  ]
}

const test = validateIt<Product>(product, [
  {
    field: "productList",
    validators: [],
    nestedValidations: [
      {
        field: 'color',
        validators: []
      }
    ]
  }
])

So getting type error and overall i am trying to find correct type for nestedValidations property, which should match interface Product

ERROR

Vladimir Štus
  • 49
  • 11

2 Answers2

2

Typescript v3.7 and later

You can achieve this with in keyword in combination with keyof. Basically you're going to "generate" all possible types for each key and typescript will find matching one

type IValidation<T> = T extends Array<infer R> ? IValidation<R> : T extends object ? {
    [K in keyof T]: {
        field: K
        nestedValidations?: IValidation<T[K]>[]
        validators?: (any | any | any)[]
    }
}[keyof T] : never

Playground link

This doesn't work in older typescript versions, because they don't allow recursive types. Link to info.
BorisTB
  • 1,686
  • 1
  • 17
  • 26
0

Maybe I don't see the big picture but I think you want to achieve this:

interface Product {
  name: string,
  id: number
}

type ValueOf<T> = T[keyof T]; // not needed

type IValidation<T> = {
  field: keyof T
  nestedValidations?: IValidation<T>[] // THIS IS IMPORTANT FOR QUESTION!
  validators?: (any | any | any)[]
}

export async function validateIt<T>(payload: T, validations: IValidation<T>[]): Promise<
  Partial<{
    [key in keyof T]: string[]
  }>
  > { 
    return Promise.resolve(payload);
  }

const product: Product = {
  id: 1,
  name: 'playstation'
}

const test = validateIt<Product>(product, [
  {
    field: "id",
    validators: [],
    nestedValidations: [
      {
        field: "name",
        validators: []
      }
    ]
  }
])

Play around here: Typescript Playground

Please note that I had to simplify your data structure since I don't know how 'IRequiredValidator' is defined.

So basically we switch from

nestedValidations?: IValidation<ValueOf<T>>[]

to

nestedValidations?: IValidation<T>[]

because you want to extract the keys of T and not the keys of ( keys of T) Since that would resolve to all the properties of the type of a value assigned to a property of T.

CKE
  • 460
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  • No IValidation[] will use just a storeProductImageList key, i need here this part StoreProductImage from export type PostStoreProductPayload = { storeProductImageList?: StoreProductImage[] } – Vladimir Štus Mar 22 '22 at 14:53
  • updated with an idea it is close but no cigar – Vladimir Štus Mar 23 '22 at 08:34
  • here it is code in sandbox https://codesandbox.io/s/0tftsf – Vladimir Štus Mar 23 '22 at 08:57
  • I was playing around with your example and came up with `type IValidation = { field: P, validators?: ..., nestedValidations?: IValidation[]; }` However, there's an issue with trying to define types and validation for types like this: what is a key of a `ProductItem[]`? `0`, `1`, `2`, ... You should try reapproaching the design with the [visitor](https://en.wikipedia.org/wiki/Visitor_pattern) pattern. – j1mbl3s Mar 23 '22 at 09:36
  • do you have some examples? – Vladimir Štus Mar 23 '22 at 12:23