typescript 返回接口的属性数据，返回类型定义

Question

I have an function where I want to query data from an data object structured by an interface. This function should resolve the property data form the data object. This is working if I have any as return type, however there should be a better approach, where the return type will be the type of the property.

Here is my approach: Coding

There I only get back an union type of all properties of the interface, however I should get back the type of the property that I want to return.

Answer 1

You should make getData generic and then reuse the generic type for both argument and return value:

interface Rofl {
  name:string,
  id:number,
}

const data: Rofl = {
  name:"lol",
  id:1,
};

function getData<T extends keyof Rofl>(property: T): Rofl[T] {
  return data[property];
}


const lol:string = getData("name");

https://www.typescriptlang.org/play?ssl=16&ssc=29&pln=16&pc=33#code/JYOwLgpgTgZghgYwgAgEoHsYBtkG8CwAUMsiHALYQBcAzmFKAOYA0RJwAJlSAK7kBG0VoQC+RIgnQg6yDnDBwqaTDgC8eNqQrUARFnRYdw9lwCMwkQG5xhGDxAIwwKckYQwAEXlwAPABVkCAAPSBAOGmQAawgAT0xlbAA+AAoAByh0VOgwGKU-AEolDGwAbT8AXQ1iZCh3HigQWW8S9MzsmPLrURsJKRl9LFp6JmR1N09vZJ0ySh18rt7pAwgAOn1GZIH5oA