AbstractControl vs FormControl

In Angular, reactive forms are a way to manage and manipulate forms in a reactive and predictable manner. FormControl and AbstractControl are both important concepts within the Angular reactive forms API.

1. AbstractControl:

• AbstractControl is a base class for form controls in Angular.
• It provides the basic functionality for form controls, such as tracking their value, validity, and user interactions.
• Both FormControl and FormGroup extend AbstractControl, making it a fundamental building block for form controls.

2. FormControl:

• FormControl is a class that extends AbstractControl and represents a single input field in a form.
• It is used to track the value and validation status of an individual form control (e.g., an input field).
• You create a FormControl instance for each input field in your form.

Differences:

Hierarchy:

• FormControl is a specific implementation of AbstractControl.
• AbstractControl serves as a more general class that is extended by both FormControl and FormGroup.

Use cases:

• AbstractControl is more of a general concept and is not directly used to represent a specific input field. It is more abstract and can be used when you need to work with a group of controls, which is common in the case of FormGroup.
• FormControl is specifically designed to represent the state and behavior of an individual form control (e.g., an input field).

Creation:

• You create a FormControl for each individual input field in your form.
• AbstractControl is not typically instantiated directly for form controls; instead, you use FormControl for individual controls and FormGroup for groups of controls.

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

@Component({
  selector: 'app-my-form',
  template: `
    <form [formGroup]="form">
      <input type="text" formControlName="userName">
    </form>
  `,
})
export class MyFormComponent {
  // Using FormControl for an individual input field
  userNameControl: FormControl = new FormControl();

  // Using AbstractControl for a group of controls
  form: FormGroup = new FormGroup({
    userName: new FormControl(),
    password: new FormControl(),
  });

  // AbstractControl can represent a group or an individual control      
  abstractControlExample: AbstractControl = this.form;
}

In summary, FormControl is a specialized implementation of AbstractControl tailored for individual form controls, while AbstractControl provides a more general representation that can be used for both individual controls and groups of controls (e.g., FormGroup).