Updating the text area value based on the selected option in a dropdown using Typescript within Angular6

I'm currently facing an issue with updating the text area value based on the selection from a dropdown menu. Below is the design of the dialog:

https://i.sstatic.net/67U1M.png

Here's the code snippet I've incorporated for this functionality:

<div class="modal-content">
<div class="modal-header">
    <h5>Send Text Message</h5>
</div>

<div class="sub-title">
  <b>SELECT MESSAGE TEMPLATE:</b>
</div>

<form>
  <div>
    <select name="textmessage" class="select" [(ngModel)]="selectedMessageContentType" (change)="getSelectedTextMessage()">
        <option *ngFor="let messageContentType of messageContentTypes" [value]="messageContentType">
          {{messageContentType.messageDescription}}
        </option>
      </select>
  </div>
  <br>
  <div>
    <textarea #textmessagecontent [(ngModel)]="selectedMessageContentType.messageContent" class="textarea" maxlength="5000" type="text" name="textmessagecontent" disabled></textarea>
  </div>
</form>

<div class="modal-footer">
  <button type="button" class="btn btn-outline-primary font-weight-bold" (click)="onSendMessageClicked()">SEND</button>
  <button type="button" class="btn btn-primary font-weight-bold" (click)="onCancelClicked()">CANCEL</button>
</div>

Below is the TypeScript component:

import { Component, ElementRef, Input, OnInit, ViewChild } from "@angular/core";
import {NgbActiveModal} from '@ng-bootstrap/ng-bootstrap';
import { IssueService } from '../../../../services/issue.service';
import { IssueTextMessageRequestInput, IssueMessageContent } from "../../../../models/inputs/issue.model";
@Component({
    selector: 'textmessage',
    templateUrl: './textmessage.component.html',
    styleUrls: ['./textmessage.component.scss']
})
export class TextMessageComponent implements OnInit {
    messageContentTypes : IssueMessageContent[] = [
        { contentId: 50, messageDescription: 'Change', messageContent: 'Change something.' },
        { contentId: 51, messageDescription: 'Send Baseline', messageContent: 'Send Base' },
        { contentId: 52, messageDescription: 'Adapter', messageContent: 'Change to Lead Wire Adapter' }
    ];
    selectedMessageContentType: IssueMessageContent;
    @Input() messageData: IssueTextMessageRequestInput;
constructor(private activeModal: NgbActiveModal, private issueService: IssueService) { }

ngOnInit() {
    this.selectedMessageContentType = this.messageContentTypes[0];
}

onCancelClicked() {
    this.activeModal.close();
}

getSelectedTextMessage() {
        debugger;
        this.textarea.nativeElement.innerText = "test";
    }

onSendMessageClicked() {
    this.messageData.message = this.getMessageContentById(this.selectedMessageContentType).messageDescription;
    console.log(this.messageData);
    /*this.issueService.processAndSendMessageWithIssueActivityTracking(messageData)
    .subscribe((resp) => {});*/
}

getMessageContentById(msgId: number) {
    return this.messageContentTypes.find(content => content.contentId === msgId);
}

}

I followed some tutorials but encountered the following problems:

  • While triggering the "onchange" event, I noticed that 'this.selectedMessageContentType' displays as [object Object] and I cannot access its properties like 'contentId'. The result is always undefined.
  • Even after changing the value of the text area to "test", the change doesn't reflect in the textarea.

Any help or guidance would be highly appreciated. Thank you in advance.

Answer №1

To ensure that each option's value is an object instead of a string, you should utilize [ngValue] instead of [value], following the guidelines outlined in the official documentation: https://angular.io/api/forms/NgSelectOption#properties. To implement this change in your specific case, modify your code as shown below:

<select name="textmessage" class="select" [(ngModel)]="selectedMessageContentType">
  <option *ngFor="let messageContentType of messageContentTypes" [ngValue]="messageContentType">
   {{messageContentType.messageDescription}}
 </option>
</select>

With this adjustment, selectedMessageContentType will now store a reference to the selected messageContentType from the dropdown list.

Furthermore, resolving this issue with the textarea value - by converting selectedMessageContentType into an object rather than a string - eliminates the need for the getSelectedTextMessage() function entirely. It is recommended to avoid directly manipulating form element values using vanilla JavaScript within Angular, especially when employing template-driven approaches like [ngModel].

You can view a demonstration of the proposed solution on StackBlitz: https://stackblitz.com/edit/angular-ivy-ytvrp2?file=src/app/app.component.html

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