I have 5 checkboxes in a FormGroup, display using ngFor, and 1 matInput that has to be a required field if any of the checkboxes is checked.

.ts

```
this.gridForm = this.fb.group({
      cbox1: [''],
      cbox2: [''],
      cbox3: [''],
      cbox4: [''],
      cbox5: [''],
      input1: ['', Validators.required] });

```

.html

```
            <div *ngFor="let table of xTables; let i = index;">
              <mat-checkbox formControlName="{{xTableKeys[i]}}">{{table}}</mat-checkbox>
            </div>
            <mat-form-field>
              <input matInput formControlName="xType" placeholder="X Type">
            </mat-form-field>

```

I've added required validators for the input, but what I need is to make it required only after any of the checkboxes is checked. Current status is I cannot submit the form unless I fill in the input, but with or without checking the checkbox.