Display and update FormGroup inside FormArray

Question

I am displaying a FormArray with an *ngFor. What i am trying to do is when i click on an item in the ngFor, to populate the with that items 'task' property.

Additionally, when i type/update the contents of input, the original form is updated/patched.

HTML:

<form [formGroup]="myForm">

    <div [id]="i" 
        class="example-box"
        *ngFor="let item of myForm.get('items').controls; let i=index;"
        (click)="updateInput(item)">
        {{item.value.task}} to be
    </div>

  <br>
  <br>

  <input formControlName="xxx" />

  <br>
  <br>

    {{ myForm.value | json}}
</form>

Component.ts:

export class CdkDragDropSortingExample { 
  nominatedArray = [];
  myForm: FormGroup;

  constructor(private fb: FormBuilder) {
    this.myForm = this.fb.group({
      title: ['title'],
      items: fb.array([
        fb.group({
          completed: fb.control(false),
          task: fb.control('Set Alarm'),
          position: fb.control(0)
        }),
        fb.group({
          completed: fb.control(false),
          task: fb.control('Brush teeth'),
          position: fb.control(1)
        }),
        fb.group({
          completed: fb.control(false),
          task: fb.control('Shower'),
          position: fb.control(2)
        }),
        fb.group({
          completed: fb.control(false),
          task: fb.control('Get ready'),
          position: fb.control(3)
        }),
        fb.group({
          completed: fb.control(false),
          task: fb.control('Have breakfast'),
          position: fb.control(4)
        })
      ])
    })
  }

  updateInput(item) {
    console.log(item);
  }    
}

Stackblitz: https://stackblitz.com/edit/angular-asevei-t5pm9u

Eliseo Eliseo · Accepted Answer · 2020-06-10T17:01:57

you can declare a variable

control:FormControl

And use in your input formControl

<input [formControl]="control" />

Simply on click

(click)="control=item.get('task')

But I think you want to "edit in place". For this you need two variables and as usually I go to make a getter to the formArray

itemSelected:number=-1;
dropping:boolean=false
get items()
{
    return (this.myForm.get('items') as FormArray)
}

Our .html is like

<form [formGroup]="myForm">
    <div cdkDropList class="example-list" (cdkDropListDropped)="drop($event)">

        <div [id]="i" class="example-box" 
      [cdkDragDisabled]="itemSelected==i"
      (cdkDragDropped)="dropping=false"
            (cdkDragMoved)="dropping=true;itemSelected=-1"
            *ngFor="let item of items.controls; let i=index;" cdkDrag>
            <span *ngIf="itemSelected!=i" style="cursor:text" 
          (click)="!dropping && focus(i)" >
        {{item.value.task}} to be
    </span>
            <input #input *ngIf="itemSelected==i" [formControl]="item.get('task')" 
           (blur)="itemSelected=-1">
    </div>
</div>
</form>

NOTE: to use the property cdkDragDisable you need updated your references, in "@angular/cdk": "7.0.3" you has not this property, so you need update to Angular 9 too

See how, if "i=selectedIndex" it's showed the "input" and the cdkDrag is disabled. We need mannage when we click and when we want to drag. for this, I use the variable dropping that is true when you move and false when dropped, moreover, we make nothing if is dropping is true, the (click)="!dropping && focus(i)"

Well, the function focus put the variable itemSelected to the value of the row and make the focus. The focus need make in a setTimeout to give a change to Angular to show the input

  focus(i:number)
  {
    this.itemSelected=i
    setTimeout(()=>{
      this.input.nativeElement.focus()
    })
  }

Finally, the drop function, need take account that the function moveItemInArray is thinking to work with arrays, not with formArrays, so

  drop(event: any) {
    const array=this.items.value //get the value of the formArray
    moveItemInArray(array, event.previousIndex, event.currentIndex); //move the value
    array.forEach((x:any,i:number)=>x.position=i)  //recalculate the position
    this.items.setValue(array)  //make a setValue
  }

You can see in this stackblitz

Display and update FormGroup inside FormArray

1 Answers