DEV Community

Cover image for Angular: An Exploration in Triggering Validation and Transformation

Posted on

Angular: An Exploration in Triggering Validation and Transformation

Recently, I came across an intriguing article about (Dynamic self-registered FormControl in Angular)(

Everything about this article was well done and very interesting.

There was one point in the article that spiked my interest: the author triggered the "creation" of the Form Controls dynamically within the Angular HTML.

So, I decided to experiment and see if I could use this as a means to trigger data validation and transformation.

This is an experiment, simple to see if I can do something. Personally, I see some benefit in the pattern. But, this does not mean I am endorsing this as a good pattern or a better means than any other way of doing something.

The working code ...

The Code

Here's the basics of the data.service.ts ...

data: Array<any> = [
  { first: 'Bob', last: 'Fornal' },
  { first: 'Jenny', last: 'Fornal' },
  { first: 'Patrick', last: 'Fornal' },
  { first: 'Anne', last: 'Fornal' }

getData = (): Array<any> =>;

validate = (item: any): boolean => item.hasOwnProperty('first') && item.hasOwnProperty('last');

transform = (item: any): any => {
  let transformed: any = Object.assign({}, item);
  if (!transformed.hasOwnProperty('fullname')) {
    transformed.fullname = item.last + ', ' + item.first;
  if (!transformed.hasOwnProperty('checked')) {
    transformed.checked = false;
  console.log(item, transformed);
  return transformed;
Enter fullscreen mode Exit fullscreen mode

My intent is to ...

  1. Get the data
  2. Display a Validation State
  3. Transform the data significantly
  4. Display the changes

The app.component.ts is really simple ...

data: Array<any>;

  private dataService: DataService
) { = [ ...this.dataService.getData() ];

validate = this.dataService.validate;
transform = this.dataService.transform;
Enter fullscreen mode Exit fullscreen mode

The code simple sets up the data and connects the validate and transform functions the the same in the dataService.

Then, in the HTML (app.component.html) ...

<div class="individual" *ngFor="let item of data;">
  <div>Validated: {{ validate(item) }}</div>

  <ng-container *ngIf="transform(item); let transformed">
    <div>Fullname: {{ transformed.fullname }}</div>
    <div>Status is False: {{ transformed.checked === false }}</div>
Enter fullscreen mode Exit fullscreen mode

Looping over the data, it gets validated, transformed, and displayed ... all exactly as expected.


This was a particularly simple experiment. To me, is shows a triggering path when dealing with data that I haven't explored before.

Generally, when I am digging into someone else's code, I am looking at the DOM (the HTML) first. In this case, being able to see the trigger points and validation processes so early could have a huge benefit.

Top comments (0)