如何为定义的接口赋值？

Question

我已经为我试图为客户端构建的响应定义了接口我看到data 有来自后端的响应，所以现在我正在尝试为我的接口对象分配值，它即将到来未定义。不知道为什么会出现这个问题？

main.ts

  private async specialtyAccountBalanceResponse(@Body()data: IAccountBalanceSdkResult): Promise<any> {
      const saveDetails = {} as ICacheRequest;
      const specialtyResponse = {} as IGetAccountBalanceResponse;

      if (!data.Details && data.Header.StatusCode !== "0000") {
          return data.Header;
      }
      specialtyResponse.details.lineOfBusiness = "SPec";
      specialtyResponse.details.balanceAccount = data.Details.balanceAccount;
      return specialtyResponse;
  }

interface.ts

export interface IGetAccountBalanceResponse {
    header: any;
    details: IGetAccountBalanceDetails;
}

export interface IGetAccountBalanceDetails {
    lineOfBusiness: string;
    balanceAccount: string;
    payment: IPaymentIndicator;
}

export interface IPaymentIndicator {
    recentPaymentIndicator: string;
    recentPaymentAmount: string;
    achAuthRequiredInd: string;
}

Answer 1

在您的示例中，您创建了一个空对象：

const specialtyResponse = {} as IGetAccountBalanceResponse;

然后你尝试访问它的一个属性：

specialtyResponse.details.lineOfBusiness = "SPec";

details 永远不会被实例化，所以它是undefined。因此您无法访问它的属性lineOfBusiness。

一种解决方案是使用@undefinedMayNotBeNull 建议的类。另一种方法是在访问属性之前设置specialtyResponse.details。

specialtyResponse.details = {} as IGetAccountBalanceDetails;

这是一个工作示例：

interface IGetAccountBalanceResponse {
    details: IGetAccountBalanceDetails;
}

interface IGetAccountBalanceDetails {
    lineOfBusiness: string;
    balanceAccount: string;
}

const specialtyResponse = {} as IGetAccountBalanceResponse;
specialtyResponse.details = {} as IGetAccountBalanceDetails;

specialtyResponse.details.lineOfBusiness = "SPec";
specialtyResponse.details.balanceAccount = "Test";

Try it on TypeScript Playground

---

更新

specialtyResponse 可能是错字。你的意思是specialityResponse吗？

Answer 2

你宁愿定义一个类而不是一个接口：

export class IGetAccountBalanceResponse {

    constructor(props?) {
       this.header = props.header;
       this.details = props.details;
    }

    public header: any;
    public details: IGetAccountBalanceDetails; 
}

然后你可以像这样实例化它：

const balance = new IGetAccountBalanceResponse()

或

const balance = new IGetAccountBalanceResponse(data)

这也有效，但除非有充分的理由，否则不应这样做

const balance: IGetAccountBalanceResponse = {} as any;

接口不应用于实例化对象，而应用于定义其类型。

如果您使用诸如 eslint 之类的 linter（我强烈建议您这样做），您会在编译之前看到错误弹出。

您可以在这里试用： http://www.typescriptlang.org/play/

Here are the official docs on it

Here is a working example