typescript - 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 a formControlName in your HTML form mapped to 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
])