How to validate the child component NgForms having 3 different NgForm from the parent component in Angular4

Question

I have a scenario where I am accessing two different NgForms one within Parent form #parentform and other in the Child component #childForm & #childForm1, and i want to check the validity of the controls of child form wether valid or not in parent component form. How to do this in angular4.

I also followed this link: Check if a form is valid from a parent component using Angular 4

everytime i am getting undefined for the reference of child component form.

My code is something like this.

parent.component.html

    <form class="form-wrapper" (ngSubmit)="parentForm.form.valid && save()" #parentForm="ngForm" novalidate>
        <input id="firstName" type="text" placeholder="" class="validate" name="firstName" [(ngModel)]="firstname_" #firstName="ngModel"                         required>
    </form>
    <child-component></child-component>

child.component.html

  <form class="form-wrapper" (ngSubmit)="childForm.form.valid && save()" #childForm="ngForm" novalidate>
            <input id="phoneNumber" type="text" placeholder="" class="validate" name="phoneNumber" [(ngModel)]="phone_" #phoneNumber="ngModel"                       required>
 </form>

 <form class="form-wrapper" (ngSubmit)="childForm1.form.valid && save()" #childForm1="ngForm" novalidate>
            <input id="mobileNumber" type="text" placeholder="" class="validate" name="mobileNumber" [(ngModel)]="mobile_" #mobileNumber="ngModel" required>
 </form>

Now i want to validate the child component form "childForm" & "childForm1" valid or not in parent form.

Same is reproduced at https://stackblitz.com/edit/angular-cjorjz...

Answer 1

So what you want, is to pass the parentForm.form.status to the child with an @Input().

In parent html:

<child-component [parent]="parentForm.form.status"></child-component>

Then in your child:

@Input() parent: any;
private boolean: boolean = false;

ngOnChanges(changes: any) {
  if(changes.dataSet.currentValue === 'VALID'){
    this.boolean = true;
  }
  else { this.boolean = false; }
}

And to check it console.log(this.boolean) it or put {{boolean}} in html. Or childForm.form.valid && save() && boolean in html.

EDIT

To send the validation back:

In the child component you have to tigger the @Output() so use a change event on the html:

@Output valid: EventEmitter<any> = new EventEmitter<any>();

private checkValid(_childForm: string){
  if(_childForm === 'VALID'){
    this.valid.emit(true);
  }
  else { this.valid.emit(false);
}

In html to all your child formsfield:

(ngModelChange)="checkValid(childForm.form.status)"

In your parent html:

<child-component [parent]="parentForm.form.status" (valid)="setValidChild($event)"></child-component>

In the parent component:

private childBoolean: boolean= false;

private setValidChild(_boolean: boolean){
  this.childBoolean = _boolean;
}