Angular 2 Form “Cannot find control with path”

Question

I try to make a dynamic form (so you can limitless add items to a list), but somehow the content of my list is not getting send because it can't find the control with path:

Cannot find control with path: 'list_items -> list_item'

My component:

@Component({
  selector: 'app-list',
  templateUrl: './list.component.html',
  styleUrls: ['./list.component.css']
})
export class ListComponent implements OnInit {

  listForm: FormGroup;

  constructor(private nodeService: NodeService, private messageService: MessageService, private fb: FormBuilder,
                private listService: ListService) { 
    this.listForm = this.fb.group({
      title: ['', [Validators.required, Validators.minLength(5)]],
      list_items: this.fb.array([
        this.initListItem(),
        ])
    });
  }


  initListItem() {
    return this.fb.group({
      list_item: ['']
    });
  }
  initListItemType() {
    return this.fb.group({
      list_item_type: ['']
    });
  }

  addListItem() {
    const control = <FormArray>this.listForm.controls['list_items'];
    control.push(this.initListItem());
  }

The Template (list.component.html):

<h2>Add List </h2>

<form [formGroup]="listForm" novalidate (ngSubmit)="addList(listForm)">
  <div class="form-group">
    <input type="text" class="form-control" formControlName="title" placeholder="Title">
  </div>

  <div formArrayName="list_items">
    <div *ngFor="let list_item of listForm.controls.list_items.controls; let i=index" class="panel panel-default">
      {{i + 1}}.) <input type="text" formControlName="list_item" placeholder="List Item" class="form-control">
    </div>
    <a (click)="addListItem()">Add List Item +</a>

  </div>

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

The title works just fine, but I can't find the error I have with the "formControlName", which is causing the error.

Thanks in advance for any help in this issue.

Update with what I changed list.component.html

<h2>Add List </h2>

<form [formGroup]="listForm" novalidate (ngSubmit)="addList(listForm)">
  <div class="form-group">
    <input type="text" class="form-control" formControlName="title" placeholder="Title">
  </div>

  <div formArrayName="list_items">
    <div *ngFor="let list_item of listForm.controls.list_items.controls; let i=index" class="panel panel-default">
      {{i + 1}}.) <input type="text" formControlName="{{i}}" placeholder="List Item" class="form-control">
    </div>
    <a (click)="addListItem()">Add List Item +</a>

  </div>

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

And in my component I changed the constructor and my addListItem method:

listForm: FormGroup;

  constructor(private nodeService: NodeService, private messageService: MessageService, private fb: FormBuilder,
                private listService: ListService) { 
    this.listForm = this.fb.group({
      title: ['', [Validators.required, Validators.minLength(5)]],
      list_items: this.fb.array([
          [''],
        ])
    });
  }

  addListItem() {
    const control = <FormArray>this.listForm.controls['list_items'];
    control.push(this.fb.control(['']));
    console.log(control)
  }

Answer 1

There should be mapped formControlName in html form & your component file.

<div *ngFor="let list_item of [0,1,2]; let i=index" class="panel panel-default">

  {{i + 1}}.) <input type="text" formControlName='{{i}}' placeholder="List Item" class="form-control">
</div>

============

list_items: this.fb.array([
 [''],  //0 points to this
 [''],  //1 points to this
 ['']   //2 points to this
])

Answer 2

Note that if your FormArray contains other FormGroup controls (which contain other instances of FormControl), you'll need to do this to access the controls inside each FormGroup:

        <div *ngFor="let item of myFormArray.controls; let i=index">
            <div formGroupName="{{i}}">
                <input formControlName="myFormGroupSubControl1" />
                <input formControlName="myFormGroupSubControl2" />

Answer 3

I also encountered this error, and I solved this problem by initiating the variables of class(elements in this.fb.array([])).

Code Snippet

    mobileNumbers: this.fb.array([this.fb.group(new MobileNumber('IN'))]),

Where class MobileNumber is used.

export class MobileNumber{
    public country_code: string;
    public mobile_number: string;
    constructor($cc){
        this.country_code = COUNTRY_CODES[$cc];
    }
}

To

export class MobileNumber{
    public country_code = '';
    public mobile_number = '';
    constructor($cc){
        this.country_code = COUNTRY_CODES[$cc];
    }
}