[英]Angular2 HTTP using observables subscribe showing data undefined
我不知道自己在做錯什么,但是以某種方式我無法讀取數據,盡管當我放入控制台時,數據是作為響應來自服務器的,甚至數據也已顯示在服務extractData方法中,但是在訂閱函數內部的組件中,它給了我未定義的信息。 幫幫我,我做錯了,我假設這是異步的問題,但是,我不知道該如何糾正。 任何幫助將是可觀的。 提前感謝
Component.ts
import { Component, Input, OnInit } from '@angular/core';
import {AdminService} from './admin.service';
import {logistics} from '../shared/model/logistics';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';
import 'rxjs/add/operator/switchMap';
import 'rxjs/add/operator/toPromise';
import { Observable } from 'rxjs/Observable';
import {Response } from '@angular/http';
@Component({
moduleId:module.id,
selector: 'admin',
templateUrl: 'admin.component.html',
styleUrls:['admin.component.css'],
providers:[AdminService]
})
export class AdminComponent implements OnInit{
@Input() public allocatedAssetsList: logistics[];
mode = 'Observable';
public errorMsg = '';
constructor(private adminService: AdminService) {
}
ngOnInit(){
this.listByEmpId("123");
}
listByEmpId(empId:string){
this.adminService.getAllocatedAssets(empId).subscribe(
res => this.allocatedAssetsList = res,
error => this.errorMessage = <any>error);
}
}
服務
import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import { Hero } from './hero';
import { Observable } from 'rxjs/Observable';
import { Headers, RequestOptions } from '@angular/http';
import {logistics} from '../shared/model/logistics';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';
import 'rxjs/add/operator/switchMap';
import 'rxjs/add/operator/toPromise';
@Injectable()
export class AdminService {
constructor (private http: Http) {}
private listAssetsURL = '/api/logistics/list/'; // URL to web API
private extractData(res: Response) {
let body = res.json();
return body || { };
}
private handleError (error: any) {
// In a real world app, we might use a remote logging infrastructure
// We'd also dig deeper into the error to get a better message
let errMsg = (error.message) ? error.message :
error.status ? `${error.status} - ${error.statusText}` : 'Server error';
console.error(errMsg); // log to console instead
return Observable.throw(errMsg);
}
getAllocatedAssets (empId: string): Observable<logistics[]> {
this.listAssetsURL+= empId;
//let body = JSON.stringify({ empId });
let headers = new Headers({ 'Content-Type': 'application/json' });
let options = new RequestOptions({ headers: headers });
return this.http.get(this.listAssetsURL)
.map(this.extractData)
.catch(this.handleError);
}
}
listByEmpId(empId:string){
this.adminService.getAllocatedAssets(empId).subscribe(
res => {
this.allocatedAssetsList = res;
console.log(this.allocatedAssetsList);
},
error => this.errorMessage = <any>error);
}
這可能是因為您試圖在實際從服務返回數據之前訪問您的locatedAssetsLists。
如果要在模板中訪問它,則可以使用簡單的ngIf
來確保僅在數據可用后才嘗試顯示它。
如果不是這樣,我們需要有關您的問題的更多信息以提供幫助。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.