Angular 2: Form containing child component

Question

I have component which has a form and some child components within the form. The child components are created using *ngFor and each child contains input elements. Angular2 compiler is giving errors like [formGroup] is not defined.

Is this implementation a correct?

Parent Component:

<section class="data-body">
        <form [formGroup]="checkoutForm" novalidate>
            <app-checkout-product-view *ngFor="let item of checkoutData.products" [_product]="item" formGroupName="products"></app-checkout-product-view>
                <div class="col-md-4">
                    <label>Nominee:</label>
                    <select required [(ngModel)]="checkoutData.selectedNominee" [ngModelOptions]="{standalone: true}">
                        <option *ngFor="let nominee of checkoutData.nomineeList" [value]="nominee">{{nominee}}</option>
                    </select>
                </div>
                <div class="col-md-4">
                    <label>Bank Account:</label>
                    <select [(ngModel)]="checkoutData.selectedBank" required [ngModelOptions]="{standalone: true}">
                        <option *ngFor="let bank of checkoutData.bankList" [value]="bank">{{bank}}</option>
                    </select>
                </div>
            </div>
        </form>
    </section>

Child Component: app-checkout-product-view

<div class="row">
    <div class="col-md-4">
        <md-input required [(ngModel)]="product.investmentAmount 
                  formControlName="investmentAmount">
            <span md-prefix>&#x20B9;</span><!--Rupee icon-->
        </md-input>
    </div>
</div>

P.S. : All the imports are fine so I am pretty sure that no import errors here

Answer 1

You're saying the imports are fine but the errors you're getting suggest that they probably are not.

[formGroup] is not defined errors are usually caused by a missing
import { ReactiveFormsModule } from '@angular/forms' inside the module where your component is declared.

Besides that, you should not use [(ngModel)] inside model-driven forms but instead rely on [formGroup] and formControlName.

Answer 2

This behavior is expected. Angular forms are not automatically registered when inside nested component. However you can workaround this by providing the outer FormGroup to the child component. And inside the child component wrap the template inside that same group. Here is how this might look:

/outer component code - it contains the form/

@Component({
  selector: 'my-app',
  template: `
    <form [formGroup]="reactiveFormGroup">
      <input formControlName="foo" />
      <my-comp **[group]="reactiveFormGroup"**></my-comp>
    </form>

    form value: {{ reactiveFormGroup.value | json }}
  `
})
export class AppComponent { 
  reactiveFormGroup = new FormGroup({
    foo: new FormControl('default foo'),
    bar: new FormControl('default bar')
  });
}

/child component code, i.e my-comp/

@Component({
  selector: 'my-comp',
  template: `
    <div [formGroup]="group">
      <input   [formControlName]="'bar'" />
    </div>
  `
})
export class MyComponent { 
  @Input() group: FormGroup;
}