Angular 6 - Multi-level nested Reactive Form duplicates inputs

Question

I have an issue related with Angular Reactive Form which I am not capable of sort out.

Code

form.html and form.ts

import {Component, OnInit} from '@angular/core';
import {FormArray, FormBuilder, FormGroup} from '@angular/forms';
import {ProcessService} from "../../../service/process.service";


@Component({
  selector: 'app-check-order-form',
  templateUrl: './check-order-form.component.html',
  styleUrls: ['./check-order-form.component.css']
})
export class CheckOrderFormComponent implements OnInit {
  submitted = false;

  X: FormGroup = this._fb.group({
    field: '',
    Y: this._fb.array([])
  });

  Yg: FormGroup = this._fb.group({
    subfield: '',
    Z: this._fb.array([])
  });

  Zg: FormGroup = this._fb.group({
    subsubfield: ''
  });

  constructor(private _fb: FormBuilder) {
  }

  ngOnInit() {
    this.createYg();
    this.createZg();
  }

  ngOnChanges() {
  }

  onSubmit(formValue) {
    this.submitted = true;
    console.warn(this.X.value);
  }

  createYg() {
    return this.Yg;
  }

  createZg() {
    return this.Zg;
  }

  
  get Y(): FormArray {
    return this.X.get('Y') as FormArray;
  }

  getCurrentZ(index): FormArray {
    return this.Y.at(index).get('Z') as FormArray;
  }
  
  addY(): void {
    this.Y.push(this.createYg());
  }

  addZ(index): void {
    let Z = this.Y.at(index).get('Z') as FormArray;
    Z.push(this.createZg());
  }


  deleteY(index) {
    this.Y.removeAt(index);
  }

  deleteZ(Yindex, index) {
    this.getcurrentZ(Yindex).removeAt(index);
  }
}

<form class="form-inline" [formGroup]="X" (ngSubmit)="onSubmit(X.value)">
  
  <div class="form-group col-3 mb-2">
    <label for="field">Field</label>
    <input type="text" class="form-control" formControlName="field" id="field">
  </div>

  <div class="form-inline" formArrayName="Y">
    <div *ngFor="let y of Y?.controls; let k=index">
      <hr/>
      <div [formGroupName]="k" class="row pt-1 pb-1">
        <div class="col-12">
          <label>Y {{k + 1}}</label>
        </div>
        <div class="form-group col-3 mb-2">
          <input type="text" class="form-control" formControlName="subfield" placeholder="subfield">
        </div>
        <div class="form-inline" formArrayName="Z">
          <div *ngFor="let fondo of getCurrentZ(k)?.controls; let j=index">
            <hr class="bg-secondary"/>
            <div [formGroupName]="j" class="pt-1 pb-1">
              <label>Z {{j + 1}}</label>
              <div class="form-group col-3 mb-2">
                <input type="text" class="form-control" formControlName="subsubfield" placeholder="subsubfield">
              </div>        
              <div class="form-group col-3 mb-2">
                <button (click)="deleteZ(k, j)" class="btn btn-danger mr-1">Remove</button>
              </div>
            </div>
          </div>
        </div>        

        <div class="form-group col-12 mb-2 pr-1">
          <button class="btn btn-info mr-1" (click)="addZ(k)">+ Z</button>
        </div>
        <div class="form-group col-12 mb-2 pr-1">
          <button (click)="deleteY(k)" class="btn btn-danger mr-1">
            Remove
          </button>
        </div>
      </div>
    </div>
  </div>

  <div class="form-group col-12 mt-2">
    <button type="submit" class="btn btn-primary mr-2">Submit</button>
    <button (click)="addY()" class="btn btn-success">+ Y</button>
  </div>
</form>

Problem

Here are the steps that lead to the issue (please, have a look at the code above, please):

1. I click on + Y button in order to add a Y FormGroup
2. I click another time on + Y
3. I click on + Z on one of the two Y FormGroup

Result: the Z FormGroup is rendered on both of the Y elements.

The ideal for me is that each FormGroup is related only with the parent one in order to compile the form properly. I tried many solutions, but I cannot find the issue despite of the specification of the index of the parent array (Y).

Thank you in advance.

Answer 1

Please check the code and I added the working module in the https://angular-4dt3sa.stackblitz.io or with code https://stackblitz.com/edit/angular-4dt3sa?file=src%2Fapp%2Fapp.component.ts

html content

<form class="form-inline" [formGroup]="X" (ngSubmit)="onSubmit(X.value)">

  <div class="form-group col-3 mb-2">
    <label for="field">Field</label>
    <input type="text" class="form-control" formControlName="field" id="field">
  </div>

  <div class="form-inline" formArrayName="Y">
    <div *ngFor="let y of Y?.controls; let k=index">
      <hr/>
      <div> test {{k}}</div>
      <div [formGroupName]="k" class="row pt-1 pb-1">
        <div class="col-12">
          <label>Y {{k + 1}}</label>
        </div>
        <div class="form-group col-3 mb-2">
          <input type="text" class="form-control" formControlName="subfield" placeholder="subfield">
        </div>
        <div class="form-inline" formArrayName="Z">
          <div *ngFor="let fondo of getCurrentZ(k)?.controls; let j=index">
            <hr class="bg-secondary"/>
            <div [formGroupName]="j" class="pt-1 pb-1">
              <label>Z {{j + 1}}</label>
              <div class="form-group col-3 mb-2">
                <input type="text" class="form-control" formControlName="subsubfield" placeholder="subsubfield">
              </div>        
              <div class="form-group col-3 mb-2">
                <button (click)="deleteZ(k, j)" class="btn btn-danger mr-1">Remove</button>
              </div>
            </div>
          </div>
        </div>        

        <div class="form-group col-12 mb-2 pr-1">
          <button class="btn btn-info mr-1" (click)="addZ(k)">+ Z</button>
        </div>
        <div class="form-group col-12 mb-2 pr-1">
          <button (click)="deleteY(k)" class="btn btn-danger mr-1">
            Remove
          </button>
        </div>
      </div>
    </div>
  </div>

  <div class="form-group col-12 mt-2">
    <button type="submit" class="btn btn-primary mr-2">Submit</button>
    <button (click)="addY()" class="btn btn-success">+ Y</button>
  </div>
</form>

Typescript

import {Component, OnInit} from '@angular/core';
import {FormArray, FormBuilder, FormGroup } from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  submitted = false;

  X: FormGroup = this._fb.group({
    field: '',
    Y: this._fb.array([])
  });

  Yg: FormGroup = this._fb.group({
    subfield: '',
    Z: this._fb.array([])
  });

  Zg: FormGroup = this._fb.group({
    subsubfield: ''
  });

  constructor(private _fb: FormBuilder) {
  }

  ngOnInit() {
    this.createYg();
    this.createZg();
  }

  ngOnChanges() {
  }

  onSubmit(formValue) {
    this.submitted = true;
    console.warn(this.X.value);
  }

  createYg() {
    return this._fb.group({
      subfield: '',
      Z: this._fb.array([])
    });
  }

  createZg() {
    return this._fb.group({
      subsubfield: ''
    });
  }


  get Y(): FormArray {
    return this.X.get('Y') as FormArray;
  }

  getCurrentZ(index): FormArray {
    return this.Y.at(index).get('Z') as FormArray;
  }

  addY(): void {
    this.Y.push(this.createYg());
  }

  addZ(index): void {
    let Z = this.Y.at(index).get('Z') as FormArray;
    let Zg = this.createZg();
    Z.push(Zg);
  }


  deleteY(index) {
    this.Y.removeAt(index);
  }

  deleteZ(Yindex, index) {
    let Z = this.Y.at(Yindex).get('Z') as FormArray;
    Z.removeAt(index);
  }
}

As LP154 mentioned . You should not create new object. @teskin

Answer 2

When you add a Y form (and a Z form), you don't create a new object but use the same one again and again (Yg and Zg). So, when you add a "new" Z on a Y form, every Y form is impacted because they are the same.

Remove Yg and Zg and replace createYg() and createZg() by this :

  createYg() {
    return this._fb.group({
      subfield: '',
      Z: this._fb.array([])
    });
  }

  createZg() {
    return this._fb.group({
      subsubfield: ''
    });
  }