generics - typescript 中的 "Generic type ' Feature<T >' requires 1 type argument(s)"是什么意思？

Question

我尝试在 typescript 中使用 GeoJson，但编译器针对这两个变量抛出错误:Generic type 'Feature<T>' requires 1 type argument(s)

  const pos = <GeoJSON.Feature>{
    "type": "Feature",
    "geometry": {
      "type": "Point",
      "coordinates": [0, 1]
    }
  };

  const oldPos = <GeoJSON.Feature>{
    "type": "Feature",
    "geometry": {
      "type": "Point",
      "coordinates": [2, 4]
    }
  };

这是什么意思？

Answer 1

Feature接口(interface)需要一个参数:

export interface Feature<T extends GeometryObject> extends GeoJsonObject
{
    geometry: T;
    properties: any;
    id?: string;
}

试试这个:

  const pos = <GeoJSON.Feature<GeoJSON.GeometryObject>>{
    "type": "Feature",
    "properties":{},
    "geometry": {
      "type": "Point",
      "coordinates": [0, 1]
    }
  };

也许引入一个辅助类型并在 pos 上设置类型而不是转换将帮助您确保设置了所需的“属性”属性:

type GeoGeom = GeoJSON.Feature<GeoJSON.GeometryObject>;
const pos: GeoGeom = {
    type: "Feature",
    properties: "foo",
    geometry: {
        type: "Point",
        coordinates: [0, 1]
    }
};