Typescript get a value with given key and object interface-CodePudding

With some basic typescript:

interface Person{
    name:string;
    favoriteColors:string[];
}
const examplePerson:Person = {
    name:"Jack",
    favoriteColors:["red","blue"],
}

I want to make a value grabber function that takes a key as a parameter and returns the value:

type ValueGetter<PInterface> = (objectKey: keyof PInterface, objectValues: PInterface) => PInterface[keyof PInterface];

const personValueGetter:ValueGetter<Person> = (objectKey: keyof Person, objectValues:Person) => objectValues[objectKey]

This code works fine for getting the actual value. However, personValueGetter(examplePerson, 'name') is typed as string|string[].

Is it possible to type this function so that is knows the correct type returned based off the key and given interface?

CodePudding user response：

That achievable by infering the return type from the key.

interface Person {
  name: string;
  favoriteColors: string[];
}
const examplePerson: Person = {
  name: "Jack",
  favoriteColors: ["red", "blue"],
}


const personValueGetter = <Person, K extends keyof Person>(objectKey: K, objectValues: Person): Person[K] => objectValues[objectKey]

const _name = personValueGetter("name", examplePerson) // string

const _favoriteColors = personValueGetter("favoriteColors", examplePerson) // string[]

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