Accessing array object inside a json to display the drop down values in Angular 5

Question

I have a json object as below :

  dataset: Dataset[] = [
  {
    serviceType: "server Mangemanet",
    serviceValues: [
      "6.2",
      "6.3",
      "6.6"
    ]
  },
  {
    serviceType: "server admin",
    serviceValues: [
      "4.1",
      "4.2",
      "4.6"
    ]
  },

];

and i have two drop downs so that the value in thesecond one should be displayed based on the value selected in first dropdown . In first drop down i will select the servicetype and in the second dropdown the corresponding service values should appear. iam trying to do it this way :

<td>
      <select [(ngModel)]="data2" placeholder="select a value" (change)="data2 = dataset[idx];" >
        <option *ngFor="let data of dataset;let idx = index;"  value= {{dataset[idx].serviceType}} >
          {{dataset[idx].serviceType}}
        </option>
      </select>
     </td>
     <td>
      <select placeholder="select a value" [(ngModel)]="data2" >
        <option *ngFor="let data of data2.serviceValues;let idx = index" value= {{data}}  >
          {{data}}
        </option>
      </select>
     </td>

But the error says : Cannot read property 'serviceValues' of undefined at Object.eval I am not able to find why it not able to read service values from the array.

Thanks

Batman25663 · Accepted Answer · 2018-05-23 11:29:54Z

Here's a working example:

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

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  constructor(){}

  data1: any;
  data2: any;
  dropdown: any[] = []; //the one which will be triggered when first dropdown is selected

  dataset: any[] = [
      { serviceType: "server Mangemanet", serviceValues: ["6.2","6.3","6.6"] },
      { serviceType: "server admin", serviceValues: ["4.1","4.2","4.6"] },
  ];


  triggerd2(event: any): void {
    this.dropdown = this.dataset.find(item=>{
      return item.serviceType == event;
    }).serviceValues;
  }

}

And the html part:

<td>
    <select [(ngModel)]="data1" placeholder="select a value" (change)="triggerd2($event.target.value)"  >
        <option *ngFor="let data of dataset;let i = index;" value={{data.serviceType}}>
            {{data.serviceType}}
        </option>
    </select>
</td><br />
<td>
   <select placeholder="select a value" [(ngModel)]="data2" >
        <option *ngFor="let data of dropdown;let idx = index" value= {{data}}  >
            {{data}}
        </option>
    </select>
</td>

Try on stackblitz here

Sangwin Gawande · Accepted Answer · 2018-05-23 10:43:58Z

1

Try Using following code :

You have used [(ngModel)]="data2" 2 times. and I have changed (change) event as well.

<td>
    <select [(ngModel)]="data1" placeholder="select a value" (change)="data2 = dataset[$event.target.value];" >
        <option *ngFor="let data of dataset;let idx = index;"  value= {{idx}}">
            {{dataset[idx].serviceType}}
        </option>
    </select>
</td>
<td *ngIf="data2">
    <select placeholder="select a value" [(ngModel)]="data2" >
        <option *ngFor="let data of data2.serviceValues;let idx = index" value= {{data}}  >
            {{data}}
        </option>
    </select>
</td>

answered May 23, 2018 at 10:43

Sangwin Gawande

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