Angular 2 Accessing Nested FormArrays in FormArrays using FormBuilder

Question

First of all I just begin with Angular 2 and I'm trying to build a nested form and validate it and add new object Projects into object GroupProject.

Here's part of my ts file:

ngOnInit() {
  this.myForm = this.formBuilder.group({
    groupproject: this.formBuilder.array([
      this.initGroupProjects()
    ])
  });
}

public initGroupProjects(): any {
    return this.formBuilder.group({
        groupproject: this.formBuilder.array([this.initProjects()])
    });
}

public initProjects(): any {
  return this.formBuilder.group({
    name: ['', [Validators.required, Validators.minLength(3)]],
    some_array: this.formBuilder.array([
      this.formBuilder.group({
        name: ['', Validators.required],
        attr: ['', Validators.required],
        some_id: [1, Validators.required]
      })
    ])
  });
}

addProject(): void {
  const control = < FormArray > this.myForm.controls['projects'];
  control.push(this.initProjects());
}

View:

<form [formGroup]="myForm" novalidate (ngSubmit)="onSubmit(myForm)">
    <div formArrayName="groupproject">
        <div [formGroupName]="gp" *ngFor="let objGroupProject of myForm.controls.groupproject.controls; let gp = index">
            <div formArrayName="projects">
                <div [formGroupName]="i" *ngFor="let project of objGroupProject.controls.projects.controls; let i = index">
                    <md-input placeholder="Name" formControlName="name"></md-input>
                    <div formArrayName="some_array">
                        <div [formGroupName]="x" *ngFor="let some_obj of project.controls.some_array.controls; let x = index">
                            <div>
                                <md-input placeholder="Nome" formControlName="name"></md-input>
                                <small *ngIf="!some_obj.controls.name.valid">Nome é requerido</small>
                            </div>
                            <md-input type="number" placeholder="Cost" formControlName="attr" required></md-input>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
    <button type="submit" md-raised-button color="primary" [disabled]="!myForm.valid">Submit</button>
</form>
<pre>form value: <br>{{myForm.value | json}}</pre>

The output of form value:

form value:

{  
   "groupproject":[  
      {  
         "projects":[  
            {  
               "name":"",
               "some_array":[  
                  {  
                     "name":"",
                     "attr":"",
                     "some_id":1
                  }
               ]
            },
            {  
               "name":"",
               "some_array":[  
                  {  
                     "name":"",
                     "attr":"",
                     "some_id":1
                  }
               ]
            }
         ]
      }
   ]
}

Well, as you can see I have some arrays called groupprojects, with 1 array inside each one.

So the problem is that I'm not able to insert object project in object groupproject

Actually I'm getting the following error:

ERROR TypeError: Cannot read property 'controls' of undefined

Answer 1

Most likely you have a type in the following code:

public initGroupProjects(): any {
    return this.formBuilder.group({
        groupproject: this.formBuilder.array([this.initProjects()])
         ^^^^^^^
    });
}

I think it should be projects instead of groupproject:

public initGroupProjects(): any {
    return this.formBuilder.group({
        projects: this.formBuilder.array([this.initProjects()])
    });
}

Check also working Plunker Example

See also

• Nested arrays in Angular 2 reactive forms?