当我有一个嵌套接口并且我只想获取 object 时，如何在 function 的参数中定义？

Question

I have a function that uses only pointData object.

interface AllTheDatas{
 id: string
 pointData: {
  square: string
  triangle: string
 }
}

I'd like to use only the pointData object, but I don't know how to type it in a function argument:

// do something
buildPointData(AllTheDatas.pointData)

function buildPointData(pointData: ?????){
 // do something

 return `${AllTheDatas.square}--${AllTheDatas.triangle}
}

I tried to use Partial, Pick<AllTheDatas, 'pointData'> but it doesn't work, returning an error expecting the 2 keys and values inside of pointData object.

I know that I can do something like {x: string, y: string} but since I have a AllTheDatas interface, can't I just try to reuse it?

Answer 1

The easiest way is to just extract the type into a separate interface and give it a proper name:

interface PointData {
  square: string;
  triangle: string;
}
interface AllTheDatas {
  id: string;
  pointData: PointData;
}

Then you can just use that named type in your function parameter declaration:

function buildPointData(pointData: PointData) {
  … // do something
}

---

An alternative is to refer to a property of the AllTheDatas type via an indexed access type expression . You can write

function buildPointData(pointData: AllTheDatas["pointData"]) {
  … // do something
}