Try to produce subset of object
type person = {name: string, age: number, dob: Date};
type p1 = Pick<person, 'name' | 'dob'>
but get error ("error dob is missing") if
person1: p1 = {name: 'test1'}
I am wondering what is the best way to create all subsets of type person in Typescript.
CodePudding user response：
Is this what you want?
type person = {name: string, age: number, dob: Date};
type PickOptional<T, K extends keyof T> = {[k in K]?:T[k]}
type Test = PickOptional<person,'name' | 'dob'>
let person1: Test = {name: 'test1'}
CodePudding user response：
The normal Pick utility type is probably not what you want as it produces a type containing all the properties specified in the union of keys. We can make our custom PickUnion which behaves differently.
type PickUnion<T, K extends keyof T> =
K extends K
? Pick<T, K>
: never
It works by distributing the result over K which leads to a union of Picks.
type P1 = PickUnion<Person, 'name' | 'dob'> & Partial<Person>
// valid
const person1: P1 = { name: 'test1' }
const person2: P1 = { dob: new Date() }
// invalid
const person3: P1 = {}