Lab 05: Custom Form Control

📖 Resources

• ControlValueAccessor Documentation
• Custom Form Controls Guide
• Components Documentation

🚀 Starter Code

step-5-album-wholesale-v16-post-add-custom-async-validator

In this lab, you'll create a reusable custom form control component by implementing the ControlValueAccessor interface. You'll build a toggle switch component that integrates seamlessly with Angular's reactive forms and can be used with formControlName.

📝 Instructions

Step 1: Implement ControlValueAccessor

Create a custom form control component:

import { Component, forwardRef } from '@angular/core';
import { NG_VALUE_ACCESSOR, ControlValueAccessor } from '@angular/forms';

@Component({
  selector: 'app-toggle-switch',
  providers: [{
    provide: NG_VALUE_ACCESSOR,
    useExisting: forwardRef(() => ToggleSwitchComponent),
    multi: true
  }]
})
export class ToggleSwitchComponent implements ControlValueAccessor {
  value: boolean = false;
  onChange = (value: boolean) => {};
  onTouched = () => {};

  writeValue(value: boolean): void {
    this.value = value;
  }

  registerOnChange(fn: any): void {
    this.onChange = fn;
  }

  registerOnTouched(fn: any): void {
    this.onTouched = fn;
  }

  toggle(): void {
    this.value = !this.value;
    this.onChange(this.value);
    this.onTouched();
  }
}

Step 2: Use in Form

Use custom component with formControlName:

<app-toggle-switch formControlName="highlighted"></app-toggle-switch>

albumForm = this.fb.group({
  highlighted: [false]
});