Angular 角度数据表中缺少字段时出错

我正在试用Angular Cli 6来评估项目的框架。我被材料数据表示例卡住了

我不知道如何处理数据json（PeriodiceElement）缺少字段的情况。例如，如果第一个json对象中缺少该字段。他给了我

symbol: 'H'

error:  Property 'symbol' is missing in symbol

该表应出现，当fiels缺失时，该表中的fiels应为空字符串或null

    import {Component} from '@angular/core';

    export interface PeriodicElement {
        name: string;
        position: number;
        weight: number;
        symbol: string;
    }

    const ELEMENT_DATA: PeriodicElement[] = [
        {position: 1, name: 'Hydrogen', weight: 1.0079, symbol: 'H'},
        {position: 2, name: 'Helium', weight: 4.0026, symbol: 'He'},
        {position: 3, name: 'Lithium', weight: 6.941, symbol: 'Li'},
        {position: 4, name: 'Beryllium', weight: 9.0122, symbol: 'Be'},
        {position: 5, name: 'Boron', weight: 10.811, symbol: 'B'},
        {position: 6, name: 'Carbon', weight: 12.0107, symbol: 'C'},
        {position: 7, name: 'Nitrogen', weight: 14.0067, symbol: 'N'},
        {position: 8, name: 'Oxygen', weight: 15.9994, symbol: 'O'},
        {position: 9, name: 'Fluorine', weight: 18.9984, symbol: 'F'},
        {position: 10, name: 'Neon', weight: 20.1797, symbol: 'Ne'},
    ];

    /**
     * @title Basic use of ``
     */
    @Component({
       selector: 'table-basic-example',
       styleUrls: ['table-basic-example.css'],
       templateUrl: 'table-basic-example.html',
    })
    export class TableBasicExample {
       displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];
        dataSource = ELEMENT_DATA;
    }

---

在您的情况下，使用带有如下可选参数的接口可能更方便

export interface PeriodicElement {
        name: string;
        position: number;
        weight: number;
        symbol?: string;
}

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一个问号就成功了。这是一个完美的答案。谢谢你@Sajeetharan。