Typescript Generics for nested array of objects-CodePudding

The

CodePudding user response：

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

CodePudding user response：

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.