响应对象中的Angular 4 Typescript解析枚举接口属性 [英] Angular 4 typescript parsing enum interface attribute in response object

问题描述

我有一个来自API的响应，该响应返回一个枚举值.从API返回的值在请求中表示为字符串. 此值是打字稿界面的enum属性.

I have a response from API which is returning a enum value. value returned from API is represented as a string in request. This value is a enum attribute of typescript interface.

问题: 收到响应时，TS接口将该值存储为字符串(可能就是问题所在)，因此我不能将其直接用作enum.

Problem: when receiving a response, TS interface store that value as a string (probably thats the issue) so i can't use it directly as enum.

obj模型:

export interface Condo {

  id:number
  title:string
  latitude:number
  longitude:number

  city:string
  country:string
  district:string
  address:string
  locationType: LocationType
}

export enum LocationType {
  CONDO,
  MALL,
  STATION
}

请求:

getCondoAllByCountry(country_code){
    return this.http.get(this.config.apiEndpoint +this.subApiUrl+'/all')
      .map(res => <Condo[]>res.json())
      .catch((err:Response) => {
        return Observable.throw(err.json());
      });
    }

使用示例:

    this.condoService.getCondoAllByCountry(this.userData.country_code).subscribe(data=>{
          someFunc(data)
        })

............
    someFunc(condo_list: Condo[]){
    //here is need to know the `locationType` for each object
      console.log(typeof condo_list[i].locationType);
      console.log(typeof LocationType.CONDO)
      switch (condo_list[i].locationType){
        case LocationType.CONDO:
          console.log('Case - condo')
          break;
        case LocationType.MALL:
          console.log('Case - mall')
          break;
        case LocationType.STATION:
          console.log('Case - station')
          break;
      }
    }

因此，switch.. case不适用于此属性.在console.log()中，我得到了:

So, the switch.. caseis not working for this attribute. in console.log() i'm getting:

console.log(typeof condo_list[i].locationType);-string

console.log(typeof LocationType.CONDO)-number

那么，这意味着存在一个解析概率，而condo_list[i].locationType不是enum(考虑它应该为枚举显示number)?

So, that means that there were a parsing prob and condo_list[i].locationType is not a enum (considering it should show number for enum)?

我应该如何解决?

推荐答案

如果使用的是打字稿2.4或更高版本，则可以声明字符串枚举，如下所示:

If you're using typescript 2.4 or above, you can declare string enums as follows:

export enum LocationType {
  CONDO = 'CONDO',
  MALL = 'MALL',
  STATION = 'STATION'
}

// ...

switch (object.locationType) {
    case LocationType.CONDO: // ...
    case LocationType.MALL: // ...
    case LocationType.STATION: // ...
}

在旧版本中，只能使用基于数字的枚举.在这种情况下，最好使用字符串文字联合类型:

In older versions, you're restricted to using number-based enums. In that case, you're probably better off using a string literal union type:

export type LocationType = 'CONDO' | 'MALL' | 'STATION';

// ...

switch (object.locationType) {
    case 'CONDO': // ...
    case 'MALL': // ...
    case 'STATION': // ...
}

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