什么意思是"Generic type'Feature <T>'在Typescript中需要1个类型的参数？"

Question

我尝试在打字稿中使用GeoJson,但编译器会为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]
    }
  };

这应该是什么意思？

Answer 1

Feature接口需要一个参数：

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

尝试这个：

  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 上设置类型而不是强制转换将帮助您确保已设置所需的“properties”属性：

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