Question

我有以下代码：

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import { map } from 'rxjs/operators';

interface SingleParamConstructor<T> {
  new (response: any): T;
  id: T;
}

@Injectable()
export class RestProvider<T> {
  baseUrl:string = "http://localhost:3000";

  constructor(private ctor: SingleParamConstructor<T>, private httpClient : HttpClient) { }

  public getEntities<T>(): Observable<T[]> {
    return this.httpClient
      .get(this.baseUrl + '/products')
      .pipe(map(entities => {
        return entities.map((entity) => new this.ctor(entity));
      }))
      .catch((err) => Observable.throw(err));

  }
}

当我尝试上面的代码时，我得到了TS2339: Property 'map' does not exist on type 'Object'。

负责的行是：return entities.map((entity) => new this.ctor(entity));

我做错了什么？如何映射entities？

Answer 1

您没有在get中告诉angular您要接收的数据类型，因此Angular会自动假定它为an anonymous object, as that is what Angular httpclient parses to the data to。也不相关，因为您使用的是rxjs 6->使用catchError而不是.catch：

import { catchError, map } from 'rxjs/operators';
import { of } from 'rxjs';

// ...

public getEntities<T>(): Observable<T[]> {
  return this.httpClient
    // note below, now angular knows it's an array!
    .get<T[]>(this.baseUrl + '/products')
    .pipe(
       map(entities => {
        return entities.map((entity) => new this.ctor(entity));
       }),
       catchError((err) => of(err))
    )
}

Answer 2

我几乎可以确定您得到的（entities）是一个不可迭代的对象。

将pipe(map更改为pipe(tap并执行console.log，以查看从服务器获取的内容，

.pipe(tap(entities => console.log(entities));

然后，如果您需要遍历对象的道具，请执行Object.keys（myObj）来返回数组。

希望这对您有帮助

TS2339：属性“地图”在类型“对象”上不存在

2 个答案: