Error when a field is missing in Angular data table

Question

I am experimenting with Angular Cli 6 to evaluate the framework for a project. I'm stuck with Material Data Table example https://material.angular.io/components/table/overview

I don't how to handle a situation if my data-json (PeriodicElement) missing a field. For example if the field

symbol: 'H'

is missing in the first json-object. Angular is giving me

error:  Property 'symbol' is missing in symbol

The table should appear and when the fiels is missing, it should be empty as empty string or null in the table.

    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;
    }

Answer 1

In your case, it might be more convenient to use an interface with optional parameter like this

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