Question

这是错误说 ＆＃34;无法读取属性＆＃39;推送＆＃39;使用下面的代码时未定义＆＃34;

  let deal = new Deal(  5, 'afaf', 'dafa',5,23 ) 
  this.publicDeals.push( deal )   // gives a error saying Cannot read property 'push' of undefined(…)

整体如下所示

export class Deal { 
  constructor(
    public id: number,
    public name: string,
    public  description: string,
    public originalPrice: number,
    public salePrice: number
      ) { }    
}

在另一个组件中，

import { Component, OnInit } from '@angular/core'; 
import { Deal } from '../deal';
import { DealService } from '../deal.service';

@Component({
  selector: 'public-deals',
  templateUrl: 'public-deals.component.html',
  styleUrls: ['public-deals.component.css']
})

export class PublicDealsComponent implements OnInit {
  publicDeals: Deal[];

  constructor(
    private dealService: DealService) {
  }

  ngOnInit(): void {    
      let deal = new Deal(  5, 'afaf', 'dafa',5,23 ) 
      this.publicDeals.push( deal )   // gives a error saying Cannot read property 'push' of undefined(…)

  }

  purchase(item){
    alert("You bought the: " + item.name);
  }
}

Answer 1

publicDeals未启动;

publicDeals: Deal[] = [];

Answer 2

你必须使用下面的方法初始化数组：

publicDeals: Deal[] = [];

或

publicDeals: Deal[] = new Array();

Answer 3

这里是数字数组：

{{1}}

Answer 4

如果您使用AngularFire5.0 在推送之前，您必须列出您的项目

const afList = afDb.list('items');
afList.push({ name: 'item' });

您应该会看到Angularfire 5.0 here

的更新

Answer 5

将元素添加到数组时，请使用以下方法。以下代码也适用于角度7和8。

const publicDeals: Deal[] = []; //initialize the array
publicDeals.push(deal);

Answer 6

配合使用

publicDeals: Deal[] = [];

我之前在初始化时遇到过同样的问题

Answer 7

我的错误是我没有正确声明数组。这是

optionsArray:any[];

应该是

optionsArayy:any=[];//(missing equal to)

注意：这会创建一个“any”类型的空数组

无法读取属性＆＃39;推送＆＃39;在angular2中未定义（...）

7 个答案: