Angular 2 : Validate child component form fields from the parent component

Question

Problem statement :

Parent component having <form> tag and some <input> tags inside it, and child component also have some <input> tags, parent component has one <submit> and we are validating form fields on submit the form.

How to validate the child component <input> fields from parent component on submit the form ?

Requirement :

If a parent component has a form containing child components with input components in their template, then these input components should be validate on click if submit from the parent component.

Findings :

There are lot of posts in SO having same problem statement but did not find any suitable solution.All the below posts validate the whole form but my requirement is to validate each field in child component.

Use model driven form. Because it will check model values not form names of input. — mukund patel
I had a very similar requirement, but quite more complex because I had to validate a hierarchy forms, children, nested components and so on. It is very easy to validate using Reactive forms approach angular.io/guide/reactive-forms — Daniel C.
Are you facing problem with plugins, like auto-complete or datepiker? — mukund patel
stackoverflow.com/a/47695731/4834833 read this. Here a piece of code which added after a given parent element. I hope something help you. — mukund patel
Can you post a sample application so we can have more context? — Immanuel Rosal

Rohit Jindal Rohit Jindal · Accepted Answer · 2018-01-06T18:26:32

We can achieve it using template driven technique as well. Find below the steps :

From parent component to child component we have to pass submit button event.
```
<button type="button" (click)="enterForm(parentForm)">Submit</button>
```
Here, parentForm is the form reference.
call child component method using @ViewChild decorator from parent to pass submit button event on click of submit.
```
@ViewChild('validateChildComponentForm') private ChildComponent: ChildComponent;
```

Pass the reference of child form using @ViewChild decorator into the child component.

@ViewChild('smartyStreetForm') form;

enterForm(parentForm) {
    this.submitted = true;
    this.ChildComponent.validateChildForm(this.submitted);
    if(!parentForm.valid || !this.childFormValidCheck) {
        return;
    } else {
       // success code comes here.
    }                
}

Now in child component method we will check that if parent form is submitted and child component form is valid then emit true otherwise false into the parent component. we will use @Output decorator to emit the isChildFormValid value into the parent component.

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

public validateChildForm(data: any) {
    if (data === true) {
        if(this.form.valid === true) {
            this.isChildFormValid.emit(true);
        } else {
            this.isChildFormValid.emit(false);
        }
    }
}

Now in parent component we will get the isChildFormValid value.

private isChildFormValid(formValid: any) {
    this.childFormValidCheck = formValid;
}

Pictorial representation :

Angular 2 : Validate child component form fields from the parent component

1 Answers