angular - 错误 TS2339 : Property 'filter' does not exist on type for custom interface

Question

我为对象数组创建了一个接口(interface)

export interface UpdateMediaList {
    [index: number]: ContactResponse;
}

interface ContactResponse {
    contactId: number;
    email: string;
    firstName: string;
    imgDisplayPath: string;
    inMediaList: true;
    jobTitle: string;
    lastName: string;
    mediaOutletId: number;
    mediaOutletName: string;
    openRate: string;
    phone: string;
    responseRate: string;
    secureRate: string;
}

然后我在我的服务中使用它......

postUpdateMediaList(param, body, url = this.urls.mediaList.updateMediaList) {
    let params = new HttpParams();
    params = params.set('sortType', param.sortType);
    params = params.set('numRows', param.numRows);
    params = params.set('startRow', param.startRow);
    return this.http.post<UpdateMediaList>(url, body, {params: params});
}

现在我收到这个错误

ERROR in src/app/modules/media-list/containers/media-list-builder/media-list-builder.component.ts(142,22): error TS2339: Property 'filter' does not exist on type 'UpdateMediaList'

在这段代码中:

this.mediaList = response
    .filter(items => items.inMediaList === true)
    .map(items => items.contactId);
while (this._contacts.value.length !== 0) {
    this._contacts.removeAt(0);
}

Answer 1

你的定义:

export interface UpdateMediaList {
    [index: number]: ContactResponse;
}

没有定义 TypeScript Array , 但只是一个带有数字键的对象，其值为 ConstactResponse对象。一个Array<T>确实有 numeric-keyed properties , 但它也有所有 Array类似 filter() 的方法，您显然依赖它。

这是满足您的 UpdateMediaList 的东西定义:

declare const someContactResponse: ContactResponse;
const weirdUpdateMediaList: UpdateMediaList = {0: someContactResponse};

如您所见，weirdUpdateMediaList具有数字键属性但不是数组。您不想允许此代码:

weirdUpdateMediaList.filter(x => true); // error at compile time

因为它会在运行时爆炸 weirdUpdateMediaList.filter is not a function .

---

假设您实际上得到了一个 Array从你的后端，那么你应该只使用 Array像这样而不是你对 UpdateMediaList 的定义:

export type UpdateMediaList = Array<ContactResponse>;

或者，等价地

export type UpdateMediaList = ContactResponse[];

然后，如果你尝试这样做，你会得到一个错误:

const weirdUpdateMediaList: UpdateMediaList = {0: someContactResponse}; 
// error!  not assignable to type 'ContactResponse[]'.
//   Property 'length' is missing in type '{ 0: ContactResponse; }'.

可以安全地假设任何 UpdateMediaList 类型的对象是实际的 Array包含您需要的所有方法。

这有意义吗？祝你好运。