Angular 2 Dynamic Nested Form

Question

Basically I want to create a dynamic form with nested objects like the picture below:

• Pay offs are in an array on the model
• We should be able to add/remove pay offs as needed.
• The form should sync underlying form controls and model
• The number of pay offs is arbitrary and should be loaded into the form from the model

There are no working examples that I could find as how to do this in Angular 2, although this was really easy to do in Angular 1.

---

Below is my original question, I've since updated it for clarification (see above):

First I just wanted to point out that I'm aware that a new version of Angular 2 rc.2 has just been released a few days ago. So the code for creating a dynamic, nested form may have changed some but there's not enough documentation to figure this out.

In the latest version(s) of Angular 2 (I'm currently using rc.1 but planning to update to rc.2) I need to create a form like this (pseudo-code of view):

<form [ngFormModel]="form" (ngSubmit)="onSubmit()">
  <input type="text" ngControl="name">

  <div *ngFor="let expense for expenses; let i = index;" control-group="expenses">
    <input type="text" ngControl="expense.amount" [(ngModel)]="myModel.expenses[i].amount"> 
    <input type="checkbox" ngControl="expense.final" [(ngModel)]="myModel.expenses[i].final"> 
  </div>

  <a class="button" (click)="addExpenseControl()">Add</a>
  <a class="button" (click)="deleteExpenseControl()">Delete</a>
</form>

So the pseudo-code above won't work but to be honest because of lack of documentation I can't figure out how to wire something like this up. There's a few tutorials about nested ControlGroup but this won't fit the case here since we need to be able to dynamically add and remove control groups, and also I need to be able to sync them with a model.

I found this plunkr here provided by Angular team which allows adding of Controls to a form--but this is not adding/removing a ControlGroup, rather it's using ControlArray and I'm not sure if that applies here?

I'm very familiar with using the newer model-based Angular 2 forms however I'm grasping for resources in order to properly nest them (dynamically!), and tie this nested data into the main form model. How would I refer to nested controls in the view? Is the pseudo-code above even close? I'd post code from my controller but honestly I wouldn't know where to start when it comes to the nested expenses (ControlGroup ??) above...

Answer 1

I had to figure this out on my own because it seems that forms are still changing in Angular 2 and I've not seen any other examples similar to this (although it seems like a very common use-case).

Here is a plunkr of working example using Angular2 RC3.

I am using updated Angular 2 form code from this document.

app.component.ts (contains the form):

import { Component } from '@angular/core';
import {REACTIVE_FORM_DIRECTIVES, FormControl, FormGroup, FormArray} from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: 'app/app.html',
  directives: [REACTIVE_FORM_DIRECTIVES],
  providers:  []
})
export class AppComponent {
  form: FormGroup;
  myModel:any;

  constructor() {
    // initializing a model for the form to keep in sync with. 
    // usually you'd grab this from a backend API
    this.myModel = {
      name: "Joanna Jedrzejczyk",
      payOffs: [
        {amount: 111.11, date: "Jan 1, 2016", final: false},
        {amount: 222.22, date: "Jan 2, 2016", final: true}
        ]
    }

    // initialize form with empty FormArray for payOffs
    this.form = new FormGroup({
      name: new FormControl(''),
      payOffs: new FormArray([])
    });

    // now we manually use the model and push a FormGroup into the form's FormArray for each PayOff
    this.myModel.payOffs.forEach( 
      (po) => 
        this.form.controls.payOffs.push(this.createPayOffFormGroup(po))
    );
  }

  createPayOffFormGroup(payOffObj) {
    console.log("payOffObj", payOffObj);
    return new FormGroup({
      amount: new FormControl(payOffObj.amount),
      date: new FormControl(payOffObj.date),
      final: new FormControl(payOffObj.final)
    });
  }

  addPayOff(event) {
    event.preventDefault(); // ensure this button doesn't try to submit the form
    var emptyPayOff = {amount: null, date: null, final: false};

    // add pay off to both the model and to form controls because I don't think Angular has any way to do this automagically yet
    this.myModel.payOffs.push(emptyPayOff);
    this.form.controls.payOffs.push(this.createPayOffFormGroup(emptyPayOff));
    console.log("Added New Pay Off", this.form.controls.payOffs)
  }

  deletePayOff(index:number) {
    // delete payoff from both the model and the FormArray
    this.myModel.payOffs.splice(index, 1);
    this.form.controls.payOffs.removeAt(index);
  }
}

Notice above that I manually push new FormGroup objects into the form.controls.payOffs array, which is a FormArray object.

app.html (contains form html):

  <form (ngSubmit)="onSubmit()" [formGroup]="form">

    <label>Name</label>
    <input type="text" formControlName="name" [(ngModel)]="myModel.name" placeholder="Name">

    <p>Pay Offs</p>
    <table class="simple-table">
      <tr>
        <th>Amount</th>
        <th>Date</th>
        <th>Final?</th>
        <th></th>
      </tr>
    <tbody>
      <tr *ngFor="let po of form.find('payOffs').controls; let i = index">
        <td>
          <input type="text" size=10 [formControl]="po.controls.amount" [(ngModel)]="myModel.payOffs[i].amount">
        </td>
        <td>
          <input type="text" [formControl]="po.controls.date" [(ngModel)]="myModel.payOffs[i].date">
        </td>
        <td>
          <input type="checkbox" [formControl]="po.controls.final" [(ngModel)]="myModel.payOffs[i].final">
        </td>
        <td>
          <button (click)="deletePayOff(i)" style="color: white; background: rgba(255, 0, 0, .5)">x</button>
        </td>
      </tr>
    </tbody>
    <tr>
      <td colspan="4" style="text-align: center; padding: .5em;">
        <button (click)="addPayOff($event)" style="color: white; background: rgba(0, 150, 0, 1)">Add Pay Off</button>
      </td>
    </tr>
    </table>

  </form>

In the html form I link the form to the model on the inputs with statements like so:

... [formControl]="po.controls.amount" [(ngModel)]="myModel.payOffs[i].amount" ...