Angular 9/8 (Reactive) Forms: How to Use FormBuilder, FormGroup and FormControl APIs by Example

In this tutorial, we'll learn to use Angular forms by creating a simple example using the reactive form approach.

We'll see how to use Angular FormBuilder, FormGroup and FormControl APIs to easily build a form.

Note: For a more complete step by step example with validation, check out Build Login & Reactive Form Example with Validation

Why Forms Are Used?

Forms are used in most web applications as they allow users to submit input when interacting with the application. Among countless use cases, they are useful for sign users in, searching for information and submitting feedback.

Angular Template-Driven Forms vs Reactive Forms

Angular provides two approaches, template-driven forms and model-driven or reactive forms, for working with forms:

• The template driven approach makes use of built-in directives to build forms such as ngModel, ngModelGroup, and ngForm available from the FormsModule module.
  
• The model driven approach of creating forms in Angular makes use of FormControl, FormGroup and FormBuilder available from the ReactiveFormsModule module.

These are the steps of this tutorial:

• Prerequisites
• Angular Forms, Step 1 — Installing Angular CLI 9
• Angular Forms, Step 2 — Initializing your Project
• Angular Forms, Step 3 — Adding a Reactive Form
• Angular Forms, Step 3.1 — Importing the ReactiveFormsModule
  
• Angular Forms, Step 3.2 — Importing FormControl and FormGroup
• Angular Forms, Step 3.3 — Creating the FormGroup
• Angular Forms, Step 3.4 — Creating the HTML Form
• Angular Forms, Step 4 — Using the FormBuilder Module
• Conclusion

Prerequisites

This tutorial assumes you already have Node.js and npm installed on your machine.

You also need to be familiar with TypeScript and the basics of Angular such as components.

Let's see how to install Angular CLI.

Angular Forms, Step 1 — Installing Angular CLI 9

In this step, we'll set up Angular CLI v9 in our development machine.

Angular CLI is built on top of Node.js so as mentionned before make sure you have it installed on your machine together with npm.

Angular CLI is the official tool for initializing and working with Angular projects.

In your terminal or command prompt run the following command:

$ npm install -g @angular/cli

This will install angular/cli v9.0.0-rc in our system.

That's it, you can now initialize your project using this tool.

Angular Forms, Step 2 — Initializing your Project

Go back to your terminal and run the following commands:

$ cd ~  
$ ng new angular-forms-example

The CLI will prompt you if You would like to add Angular routing. You can type Yes if you need routing in your example and which stylesheet format you would like to use. You can select CSS.

Angular CLI will prepare your project, next you can navigate to your project's folder and serve your app locally using a development server as follows

$ cd angular-forms-example
$ ng serve

Your web application will be available from the http://localhost:4200/ address.

Go to web browser and navigate to the http://localhost:4200/ address:

Angular Forms, Step 3 — Adding a Reactive Form

In this step, we'll create an example HTML form. Next, we'll create a form model in the application component using the FormGroup and FormControl APIs. Finally, we'll use the formGroup, formControlName and formGroupName directives to bind our form model to our HTML form.

Angular Forms, Step 3.1 — Importing the ReactiveFormsModule

Open the src/app/app.module.ts file and import the ReactiveFormsModule as follows:

import { ReactiveFormsModule } from '@angular/forms';

imports: [
  ...   
  ReactiveFormsModule
],

Angular Forms, Step 3.2 — Importing FormControl and FormGroup

Next, let's import the FormControl and FormGroup classes in the src/app/app.component.ts file.

import { Component } from '@angular/core';
import { FormControl, FormGroup } from '@angular/forms';

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

Angular Forms, Step 3.3 — Creating the FormGroup

Next, let's create an exampleForm instance of FormGroup with two firstName and lastName form controls as follows:

import { Component } from '@angular/core';
import { FormControl, FormGroup } from '@angular/forms';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'app';
  exampleForm = new FormGroup ({
    firstName: new FormControl(),
    lastName: new FormControl(),

  });
}

Angular Forms, Step 3.4 — Creating the HTML Form

Next, we need to create an HTML form in the src/app/app.component.html file:

<h1>Angular 9 Forms Example</h1>
<form [formGroup]="exampleForm">
  <div class="form-group">
    <label>First Name:</label>
      <input class="form-control" formControlName="firstName">
    <label>Last Name:</label>
          <input class="form-control" formControlName="lastName">
  </div>
</form>

We use the formGroup property in the <form> tag to bind the form with our exampleForm form group and we use the formControlName property to bind the <input> tags to individual form controls.

Angular Forms, Step 4 — Using the FormBuilder Module

The FormBuilder helps you create reqctive forms using a simple functional API.

Inside the src/app/ap.component.ts file import the FormBuilder class from the @angular/forms package as follows:

import { Component } from '@angular/core';
import { FormControl, FormGroup, FormBuilder } from '@angular/forms';

Next inject FormBuilder in the component constructor as formBuilder

@Component({ selector: 'app-root', 
templateUrl: './app.component.html', 
styleUrls: ['./app.component.css'] }) 
export class AppComponent { 
title = 'app'; 
exampleForm = new FormGroup ({ firstName: new FormControl(), lastName: new FormControl()});

constructor(private formBuilder: FormBuilder) { } 
}

Next add a createForm() method with the following code:

createForm() {
    this.exampleForm = this.formBuilder.group({
      firstName: '',
      lastName: ''
    });
}

Finally call the method from the constructor:

  constructor(private formBuilder: FormBuilder) { 
      this.createForm();
  }

Conclusion

In this tutorial, we've seen a simple example of creating a form model and bind it to the HTML <form> element using Angular FormBuilder, FormGroup and FormControl APIs.

• Date: 30 Dec 2019