“类型‘对象’不可分配给类型"使用新的 HttpClient/HttpGetModule [英] "Type 'Object' is not assignable to type" with new HttpClient / HttpGetModule

问题描述

遵循 Google 的官方 Angular 4.3.2 文档在这里，我能够做一个简单的 从本地 json 文件获取 请求.我想练习从 JSON 占位符站点点击真正的端点，但我无法弄清楚要在 .subscribe() 运算符中放入什么.我制作了一个 IUser 接口来捕获有效负载的字段，但是带有 .subscribe(data => {this.users = data}) 的行抛出错误 <代码>类型对象"不可分配给类型IUser[]".处理这个问题的正确方法是什么?看起来很基本，但我是个菜鸟.

Following Google's official Angular 4.3.2 doc here, I was able to do a simple get request from a local json file. I wanted to practice hitting a real endpoint from JSON placeholder site, but I'm having trouble figuring out what to put in the .subscribe() operator. I made an IUser interface to capture the fields of the payload, but the line with .subscribe(data => {this.users = data}) throws the error Type 'Object' is not assignable to type 'IUser[]'. What's the proper way to handle this? Seems pretty basic but I'm a noob.

我的代码如下:

import { Component, OnInit } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { IUsers } from './users';

@Component({
  selector: 'pm-http',
  templateUrl: './http.component.html',
  styleUrls: ['./http.component.css']
})
export class HttpComponent implements OnInit {
  productUrl = 'https://jsonplaceholder.typicode.com/users';
  users: IUsers[];
  constructor(private _http: HttpClient) { }

  ngOnInit(): void {    
    this._http.get(this.productUrl).subscribe(data => {this.users = data});
  }

}

推荐答案

您实际上在这里有一些选择，但使用泛型将其转换为您期望的类型.

You actually have a few options here, but use generics to cast it to the type you're expecting.

   // Notice the Generic of IUsers[] casting the Type for resulting "data"
   this.http.get<IUsers[]>(this.productUrl).subscribe(data => ...

   // or in the subscribe
   .subscribe((data: IUsers[]) => ...

另外，我建议在您的模板中使用异步管道来自动订阅/取消订阅，特别是如果您不需要任何花哨的逻辑，并且您只是映射值.

Also I'd recommend using async pipes in your template that auto subscribe / unsubscribe, especially if you don't need any fancy logic, and you're just mapping the value.

users: Observable<IUsers[]>; // different type now

this.users = this.http.get<IUsers[]>(this.productUrl);

// template:
*ngFor="let user of users | async"

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