Real-world Examples of Angular Forms and Validation: How These Angular Developers Solved Common Challenges

As an Angular developer, one of the essential skills you need to master is working with forms and validation.
    Whether
    you're building a simple contact form or a complex data entry form, having a solid understanding of how to
    implement
    forms and validation in Angular is crucial. In this article, we'll explore some real-world examples of Angular
    forms
    and validation and how developers overcame common challenges.

## 1. Simple Contact Form


Let's start with a simple contact form. In this example, we want to collect the user's name, email address, and
    message.
    Angular provides two-way data binding that allows us to bind form inputs directly to variables in our
    component.

<pre><code>&lt;input type="text" [(ngModel)]="name" name="name" required&gt;</code></pre>

The `[(ngModel)]` syntax handles both reading and writing the value of the input element. The
    `name`
    attribute is used for validation, and the `required` attribute ensures that the user must provide a
    value.

## 2. Form Validation


Next, let's discuss form validation. Angular provides several built-in validators that we can use to validate
    form inputs.
    For example, to validate an email address, we can use the `EmailValidator` class.

<pre><code>import { FormControl, Validators } from '@angular/forms';

email = new FormControl('', [Validators.required, Validators.email]);</code></pre>

In this example, we create a new `FormControl` instance for the email input with two validators:
    `required`
    and `email`. If the input value is empty or not a valid email address, the form will be considered
    invalid.

## 3. Custom Validators


Sometimes, the built-in validators may not be enough for our specific requirements. In such cases, we can create
    custom
    validators to validate the form inputs. Let's say we want to create a custom validator that checks if the value
    entered
    in a password input contains at least one uppercase letter.

<pre><code>import { AbstractControl, ValidatorFn } from '@angular/forms';

export function uppercaseValidator(control: AbstractControl): { [key: string]: any } | null {
    const value = control.value;
    if (value && !/[A-Z]/.test(value)) {
        return { 'uppercase': true };
    }
    return null;
}</code></pre>
In this example, we define a custom validator function `uppercaseValidator` that takes an
    `AbstractControl` as a parameter. Inside the function, we check if the input value contains at least
    one
    uppercase letter using a regular expression. If the condition is not met, we return an object with the
    `uppercase`
    property set to `true` to indicate that the form is invalid. Otherwise, we return `null`
    to indicate
    that the form is valid.

## 4. Async Validation


In some cases, we may need to perform server-side validation or make an asynchronous call to validate a form
    input. Angular
    provides a way to handle async validation using the `AsyncValidator` interface.

<pre><code>import { FormControl, AsyncValidatorFn } from '@angular/forms';
import { Observable } from 'rxjs';

export function uniqueEmailValidator(emailService: EmailService): AsyncValidatorFn {
    return (control: FormControl): Observable&lt;{ [key: string]: any } | null&gt; => {
        const value = control.value;
        return emailService.checkEmailAvailability(value).pipe(
            map(isAvailable => {
                return isAvailable ? null : { 'notAvailable': true };
            })
        );
    }
}</code></pre>

In this example, we create a custom async validator function `uniqueEmailValidator` that takes an
    email service as a parameter. Inside the function, we return a function that takes a `FormControl`
    and returns
    an `Observable` of an object with the `notAvailable` property set to `true` if
    the
    email is not available. We use the `map` operator to transform the result of the server-side
    validation into
    the expected format.

## 5. Form Submission


Finally, let's discuss form submission. In Angular, we can handle form submission using the `ngSubmit`
    directive.

<pre><code>&lt;form (ngSubmit)="onSubmit()"&gt;
  &lt;!-- form inputs --&gt;
  &lt;button type="submit"&gt;Submit&lt;/button&gt;
&lt;/form&gt;</code></pre>

In this example, when the user clicks the submit button, the `onSubmit()` method in our component will
    be called.
    Inside this method, we can handle the form submission logic, such as sending the data to a server or performing
    any
    necessary actions.

## Conclusion


Working with forms and validation is a critical part of developing Angular applications. By understanding and
    implementing
    these common form and validation techniques, you'll be able to create robust and user-friendly forms that meet
    your
    application's requirements. Remember to combine built-in validators with custom validators and handle
    asynchronous form
    validation when necessary. With practice and experience, you'll become a proficient Angular developer when it
    comes to
    forms and validation.