在Angular 2中合并对象[重复]
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【中文标题】在Angular 2中合并对象[重复]【英文标题】:Merge objects in Angular 2 [duplicate] 【发布时间】:2017-06-05 06:18:59 【问题描述】:我无法合并 3 个对象数组。我的目标是将 3 个数组合并为一个并将 HTTP POST 发送到服务器。
我曾尝试使用 concat,但出现此错误:
例外:./PreviewEmailPage 类 PreviewEmailPage_Host 中的错误 - 内联模板:0:0 原因:无法读取未定义的属性“concat”
这些是我的代码:
import Component from '@angular/core';
import NavParams, NavController, LoadingController from 'ionic-angular';
import Validators, FormGroup, FormControl from '@angular/forms';
import Http, Headers from '@angular/http';
import 'rxjs/add/operator/map';
import Storage from '@ionic/storage';
@Component(
selector: 'preview-email-page',
templateUrl: 'preview-email.html',
)
export class PreviewEmailPage
headers: Headers;
loading: any;
url: string;
preview: any[];
FirstArray: any[];
SecondArray: any[];
ThirdArray: any[];
PostData: any[];
constructor(
public nav: NavController,
public navParams: NavParams,
public loadingCtrl: LoadingController,
public localStorage: Storage,
public http: Http,
)
this.localStorage.get('FirstArray').then((value) =>
this.FirstArray= value;
)
this.localStorage.get('SecondArray').then((value) =>
this.SecondArray= value;
)
this.localStorage.get('ThirdArray').then((value) =>
this.ThirdArray= value;
)
this.PostData = this.FirstArray.concat(this.SecondArray);
this.PostData = this.PostData.concat(this.ThirdArray);
this.loading = this.loadingCtrl.create();
ionViewWillEnter()
this.headers = new Headers();
this.headers.append("Content-Type", "application/x-www-form-urlencoded");
console.log(this.PostData);
this.getPreview();
getPreview()
this.loading.present();
this.url = 'https://domain.com/REST/getpreview.php';
this.http.post(this.url, this.PostData, headers: this.headers).map(res => res.json()).subscribe(res =>
console.log(res);
this.preview = res;
, err =>
console.log('error');
)
【问题讨论】:
正如.get(...).then(...)
所建议的,您从本地存储中获取数据是异步进行的。因此,当您进行串联时,这些字段尚未设置。
【参考方案1】:
由于this.localStorage.get
是一个异步操作,所以在执行then
之前,您的this.FirstArray
不会被定义。
您可以做的是与Promise.all
并行运行它们:
Promise.all([this.localStorage.get('FirstArray'), this.localStorage.get('SecondArray'), this.localStorage.get('ThirdArray')]).then(values =>
this.FirstArray= values[0];
this.SecondArray= values[1];
this.ThirdArray= values[2];
this.PostData = this.FirstArray.concat(this.SecondArray);
this.PostData = this.PostData.concat(this.ThirdArray);
);
【讨论】:
感谢您的回答,但现在出现此错误:异常:未捕获(承诺中):TypeError:无法读取未定义的属性“concat” @RedzwanLatif 您的回调是否返回所需的值? console.log 在回调中记录它们以查看它们返回的内容。以上是关于在Angular 2中合并对象[重复]的主要内容,如果未能解决你的问题,请参考以下文章