Angular. How to validate input in child component?

Question

Angular

Good day!

There is such a problem. It is necessary to validate the form, but the problem is that the inputs are placed in separate components in which the logic necessary for business is hidden. How to validate inputs in child components?

Patent.html

<form [formGroup]="form" (ngSubmit)="submit()">
  <input type="text" name="one" formControlName="one"><br><br>
  <app-childten formControlName="two"></app-childten>
  <button>Send</button>
</form>

parent.ts

form: FormGroup

  ngOnInit() {
    this.form = new FormGroup({
      one: new FormControl('', [Validators.required]),
      two: new FormControl('', [Validators.required]),
    })
  }

  submit() {
    console.log(this.form)
  }

childten.html

<input type="text" name="two" formControlName="two">

Answer 1

1. https://medium.com/@a.yurich.zuev/angular-nested-t...
2. or explicitly pass `form` to children