Angular 4 Observable服务不能用于api http得到
问题描述:
Angular 4 Observable服务不能用于api http get。Angular 4 Observable服务不能用于api http得到
返回observable的http似乎不起作用。
我使用的是新的HttpClient
这是错误我得到:
Error: Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays.
解决方案?
It doesn't seem to like Observable going to the ngFor. Maybe I need to do a switchMap? in the component.
这是我的HTTP服务电话:
import { Injectable } from "@angular/core";
import { HttpClient } from "@angular/common/http";
import { Observable } from "rxjs/Observable";
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/retry';
import { User } from "../models/user.model";
@Injectable()
export class UserService {
private baseUrl = "http://jsonplaceholder.typicode.com/users";
constructor(private http: HttpClient) {
}
getUsers(): Observable<User[]> {
return this.http.get<User[]>(this.baseUrl)
.retry(2)
.catch(e => this.handleError("Get Users Error", e));
}
private handleError(errorMessage: string, error: Object): any {
console.log(errorMessage, error);
}
};
这是我的html:
<div class="column" *ngFor="let user of listOfUsers | async; let i = index">
<p>{{i + 1}}.{{user.name}}</p>
</div>
这是我的组件:
import { Component, OnInit } from "@angular/core";
import { Observable } from "rxjs/Observable";
import 'rxjs/add/operator/do';
import { UserService } from "../../services/user.service";
import { User } from "../../models/user.model";
@Component({
selector: "home-users",
templateUrl: "./home.component.html"
})
export class HomeComponent implements OnInit {
private listOfUsers: Observable<User[]>;
loading: boolean;
constructor(private userService: UserService) {}
ngOnInit() {
this.getUsers();
}
getUsers(): void {
this.loading = true;
this.listOfUsers = this.userService.getUsers().do(_ => this.loading = false);
}
}
这是我的模型:
export class User {
name: string;
};
答
执行以下更改:
export interface User {
name: string;
};
@Injectable()
export class UserService {
private baseUrl = "http://jsonplaceholder.typicode.com/users";
constructor(private http: HttpClient) {
}
getUsers(): Observable<User[]> {
return this.http.get<User[]>(this.baseUrl)
.retry(2)
.catch(e => this.handleError("Get Users Error", e));
}
private handleError(errorMessage: string, error: HttpErrorResponse | any){
console.log(errorMessage, error);
}
}
新HttpClient
犯规定义一个JSON方法的Response
类。现在开发人员可以使用带有类型参数的HTTP方法。
这是我的控制台错误的屏幕截图:
答
当然,如果你改变你的主页组件以下内容,将解决你的问题?
getUsers(): void {
this.loading = true;
this.userService.getUsers().subscribe((users) => {
// --> Observable<T> returns here
this.listOfUsers = users; // or if json: this.listOfUsers = users.json();
},
(errors) => {
// --> Errors are returned here
},
() => {
// --> always called when finished
this.loading = false;
});
}
编辑
你必须为异步返回的数据映射:
this.listOfUsers = this.userService.getUsers().map((data)=> return data.json() || []);
this.works在我身边很好,看看这篇文章:angular-2-async-pipe-example
如果您使用angualr 4.3,则使用以下教程https://angular.io/guide/http,因为HttpClient不需要地图和json。 –