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, Dec 26 '17 at 17:14
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 https://angular.io/guide/reactive-forms — Daniel C., Dec 26 '17 at 17:27
Are you facing problem with plugins, like auto-complete or datepiker? — mukund patel, Dec 26 '17 at 17:39
https://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, Dec 26 '17 at 17:44
Can you post a sample application so we can have more context? — Immanuel Rosal, Dec 28 '17 at 10:57
@mukundpatel I achieve that using template driven technique as well . please look into the solution. — Debug Diva, Jan 07 '18 at 06:37
Nice use. I get more information from your given solution. It is a good chaining of events. — mukund patel, Jan 07 '18 at 07:29
@DanielC. I tried to achieve that using template driven forms technique. please look into my solution. It is working like a champ. Thanks — Debug Diva, Jan 07 '18 at 17:18

score 16 · Accepted Answer · answered Jan 06 '18 at 18:26

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 :

A lot of code to achieve this. feels like this should be more simple. — MaxwellLynn, Feb 12 '18 at 15:31
Can you please provide your more simple solution as an answer in this post. — Debug Diva, Feb 12 '18 at 16:19
Well I actually didn't have one... I was just saying it should be more simple. Although I am currently reading through this article that looks rather promising. — MaxwellLynn, Feb 12 '18 at 16:24
https://blog.thoughtram.io/angular/2016/07/27/custom-form-controls-in-angular-2.html#understanding-controlvalueaccessor — MaxwellLynn, Feb 12 '18 at 16:25

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

1 Answers1