Angular2 nested template driven form

Question

This is just madness , looks like there is no way to have a form which one of it's inputs is in a child component .

I have read all the blogs and tutorials and everything , no way to work this out .

The problem is when a child component is going to have any kind of form directives ( ngModel , ngModelGroup or whatever ..) , it wont work.

This is only a problem in template driven forms

This is the plunker :

import { Component } from '@angular/core';

@Component({
  selector: 'child-form-component',
  template: ` 
  <fieldset ngModelGroup="address">
    <div>
      <label>Street:</label>
      <input type="text" name="street" ngModel>
    </div>
    <div>
      <label>Zip:</label>
      <input type="text" name="zip" ngModel>
    </div>
    <div>
      <label>City:</label>
      <input type="text" name="city" ngModel>
    </div>
  </fieldset>`
})

export class childFormComponent{


}

@Component({
  selector: 'form-component',
  directives:[childFormComponent],
  template: `
    <form #form="ngForm" (ngSubmit)="submit(form.value)">
      <fieldset ngModelGroup="name">
        <div>
          <label>Firstname:</label>
          <input type="text" name="firstname" ngModel>
        </div>
        <div>
          <label>Lastname:</label>
          <input type="text" name="lastname" ngModel>
        </div>
      </fieldset>

      <child-form-component></child-form-component>

      <button type="submit">Submit</button>
    </form>

    <pre>
      {{form.value | json}}
    </pre>

    <h4>Submitted</h4>
    <pre>    
      {{value | json }}
    </pre>
  `
})
export class FormComponent {

  value: any;

  submit(form) {
    this.value = form; 
  }
}

Answer 1

One simple solution is providing ControlContainer in viewProviders array of your child component like:

import { ControlContainer, NgForm } from '@angular/forms';

@Component({
 ...,
 viewProviders: [ { provide: ControlContainer, useExisting: NgForm } ]
})
export class ChildComponent {}

Stackblitz Example

Read also this article that explains why it's working.

• Angular: Nested template driven form

Update

If you're looking for nested model driven form then here is the similar approach:

@Component({
  selector: 'my-form-child',
  template: `<input formControlName="age">`,
  viewProviders: [
    {
      provide: ControlContainer,
      useExisting: FormGroupDirective
    }
  ]
})
export class ChildComponent {
  constructor(private parent: FormGroupDirective) {}

  ngOnInit() {
    this.parent.form.addControl('age', new FormControl('', Validators.required))
  }
}

Ng-run Example

Update 2

If you don't know exactly which type of ControlContainer wraps your custom component(for example your controls is inside FormArray directive) then just use common version:

import { SkipSelf } from '@angular/core';
import { ControlContainer} from '@angular/forms';

@Component({
 ...,
 viewProviders: [{
   provide: ControlContainer,
   useFactory: (container: ControlContainer) => container,
   deps: [[new SkipSelf(), ControlContainer]],
 }]
})
export class ChildComponent {}

Ng-run Example

Answer 2

Another possible workaround:

@Directive({
    selector: '[provide-parent-form]',
    providers: [
        {
            provide: ControlContainer,
            useFactory: function (form: NgForm) {
                return form;
            },
            deps: [NgForm]
        }
    ]
})
export class ProvideParentForm {}

Just place this directive in a child component somewhere at the top of nodes hierarchy (before any ngModel).

How it works: NgModel qualifies parent form's dependency lookup with @Host(). So a form from a parent component is not visible to NgModel in a child component. But we can inject and provide it inside a child component using the code demonstrated above.

Answer 3

I've created a solution using a directive and service. Once you add those to your module, the only other code change you need to make are at the form level in the templates. This works with dynamically added form fields and AOT. It also supports multiple unrelated forms on a page. Here's the plunker: plunker.

It uses this directive:

import { Directive, Input } from '@angular/core';
import { NgForm } from '@angular/forms';
import { NestedFormService } from './nested-form.service';

@Directive({
    selector: '[nestedForm]',
    exportAs: 'nestedForm'   
})
export class NestedFormDirective {    
    @Input('nestedForm') ngForm: NgForm;
    @Input() nestedGroup: string;
       
    public get valid() {
        return this.formService.isValid(this.nestedGroup);
    }

    public get dirty() {
        return this.formService.isDirty(this.nestedGroup);
    }

    public get touched() {
        return this.formService.isTouched(this.nestedGroup);
    }
    
    constructor(      
        private formService: NestedFormService
    ) { 
        
    }

    ngOnInit() {   
        this.formService.register(this.ngForm, this.nestedGroup);
    }

    ngOnDestroy() {
        this.formService.unregister(this.ngForm, this.nestedGroup);
    } 

    reset() {
        this.formService.reset(this.nestedGroup);
    }
}

And this service:

import { Injectable } from '@angular/core';
import { NgForm } from '@angular/forms';

@Injectable()
export class NestedFormService {

    _groups: { [key: string] : NgForm[] } = {};
      
    register(form: NgForm, group: string = null) {           
        if (form) {
            group = this._getGroupName(group);
            let forms = this._getGroup(group);        
            if (forms.indexOf(form) === -1) {
                forms.push(form);
                this._groups[group] = forms;
            }
        }
    }

    unregister(form: NgForm, group: string = null) {        
        if (form) {
            group = this._getGroupName(group);
            let forms = this._getGroup(group);
            let i = forms.indexOf(form);
            if (i > -1) {
                forms.splice(i, 1);
                this._groups[group] = forms;
            }
        }
    }

    isValid(group: string = null) : boolean {   
        group = this._getGroupName(group);         
        let forms = this._getGroup(group);
       
        for(let i = 0; i < forms.length; i++) {
            if (forms[i].invalid)
                return false;
        }
        return true;
    } 

    isDirty(group: string = null) : boolean {   
        group = this._getGroupName(group);         
        let forms = this._getGroup(group);
       
        for(let i = 0; i < forms.length; i++) {
            if (forms[i].dirty)
                return true;
        }
        return false;
    } 

    isTouched(group: string = null) : boolean {   
        group = this._getGroupName(group);         
        let forms = this._getGroup(group);
       
        for(let i = 0; i < forms.length; i++) {
            if (forms[i].touched)
                return true;
        }
        return false;
    } 

    reset(group: string = null) {
        group = this._getGroupName(group);         
        let forms = this._getGroup(group);
       
        for(let i = 0; i < forms.length; i++) {
            forms[i].onReset();
        }
    }

    _getGroupName(name: string) : string {
        return name || '_default';
    }

    _getGroup(name: string) : NgForm[] {        
        return this._groups[name] || [];
    }          
}

To use the directive in a parent component with a form:

import { Component, Input } from '@angular/core';
import { Person } from './person.model';

@Component({
    selector: 'parent-form',
    template: `  
        <div class="parent-box">

            <!--
            ngForm                        Declare Angular Form directive
            #theForm="ngForm"             Assign the Angular form to a variable that can be used in the template
            [nestedForm]="theForm"        Declare the NestedForm directive and pass in the Angular form variable as an argument
            #myForm="nestedForm"          Assign the NestedForm directive to a variable that can be used in the template
            [nestedGroup]="model.group"   Pass a group name to the NestedForm directive so you can have multiple forms on the same page (optional).
            -->

            <form 
                ngForm                  
                #theForm="ngForm" 
                [nestedForm]="theForm"
                #myForm="nestedForm" 
                [nestedGroup]="model.group">        

                <h3>Parent Component</h3> 
                <div class="pad-bottom">
                    <span *ngIf="myForm.valid" class="label label-success">Valid</span>
                    <span *ngIf="!myForm.valid" class="label label-danger">Not Valid</span>
                    <span *ngIf="myForm.dirty" class="label label-warning">Dirty</span>    
                    <span *ngIf="myForm.touched" class="label label-info">Touched</span>    
                </div> 

                <div class="form-group" [class.hasError]="firstName.invalid">
                    <label>First Name</label>
                    <input type="text" id="firstName" name="firstName" [(ngModel)]="model.firstName" #firstName="ngModel" class="form-control" required />
                </div>

                <child-form [model]="model"></child-form>
               
                <div>
                    <button type="button" class="btn btn-default" (click)="myForm.reset()">Reset</button>
                </div>
            </form>   
        </div>
    `
})
export class ParentForm {   
    
    model = new Person();
   
}

Then in a child component:

import { Component, Input } from '@angular/core';
import { Person } from './person.model';

@Component({
    selector: 'child-form',
    template: `  
        <div ngForm #theForm="ngForm" [nestedForm]="theForm" [nestedGroup]="model.group" class="child-box">
            <h3>Child Component</h3>
            <div class="form-group" [class.hasError]="lastName.invalid">
                <label>Last Name</label>
                <input type="text" id="lastName" name="lastName" [(ngModel)]="model.lastName" #lastName="ngModel" class="form-control" required />
            </div>
        </div>  
    `
})
export class ChildForm {    
    @Input() model: Person;
      
}

Answer 4

From official docs: This directive can only be used as a child of NgForm.

So I think you can try to wrap your child component in different ngForm, and expect in parent component result @Output of child component. Let me know if you need more clarification.

UPDATE: Here is Plunker with some changes, I converted child form to model driven, because there is no way to listen on form driven form for updated before it will be submited.

Answer 5

Reading through a bunch of related github issues [1] [2], I haven't found a straightforward way to make angular add a child Component's controls to a parent ngForm (some people also call them nested forms, nested inputs or complex controls).

So what I'm going to show here is a workaround that works for me, using separate ngForm directives for parents and childs. It's not perfect, but it gets me close enough that I stopped there.

I declare my childFormComponent with an ngForm directive (i.e. it's not a html form tag, only the directive):

<fieldset ngForm="addressFieldsForm" #addressFieldsForm="ngForm">
  <div class="form-group">
    <label for="email">Email</label>
    <input type="email" class="form-control" [(ngModel)]="model.email" name="email" #email="ngModel" required placeholder="Email">
  </div>
  ...

The Component then exposes the addressFieldsForm as a property, and also exports itself as a template reference variable:

@Component({
  selector: 'mst-address-fields',
  templateUrl: './address-fields.component.html',
  styleUrls: ['./address-fields.component.scss'],
  exportAs: 'mstAddressFields'
})
export class AddressFieldsComponent implements OnInit {
  @ViewChild('addressFieldsForm') public form: NgForm;
  ....

The parent form can then use the child form component like this:

  <form (ngSubmit)="saveAddress()" #ngFormAddress="ngForm" action="#">
    <fieldset>
      <mst-address-fields [model]="model" #addressFields="mstAddressFields"></mst-address-fields>
      <div class="form-group form-buttons">
        <button class="btn btn-primary" type="submit" [disabled]="!ngFormAddress.valid || !addressFields.form.valid">Save</button>
      </div>
    </fieldset>
  </form>

Note that the submit button explicitly checks valid state on both the ngFormAddress and the addressFields form. That way I can at least sensibly compose complex forms, even though it has some boilerplate.