a FormControl exist you has a input or not. I wrote yet in another answer (but I can not find it). Use a input with [ngModel] and (ngModelChange) to control the value of FormControl
<input type="checkbox" [ngModel]="form.get('result_info2').value=='A'"
(ngModelChange)="form.get('result_info2').setValue($event?'A':'B')"
[ngModelOptions]="{standalone:true}">
If you use mat-checkbox use checked and change
<mat-checkbox [checked]="form.get('result_info').value=='A'"
(change)="form.get('result_info').setValue($event.checked?'A':'B')">
</mat-checkbox>
In a FormArray it's the same imagine you has a form with a formArray, you defined in your .ts a function taht return the formArray
get myformArray()
{
return this.form.get('formArray') as FormArray
}
And your form like
<form [formGroup]="form">
<div formArrayName="formArray">
<div *ngFor="let group of myformArray.controls;let i=index" [formGroupName]="i">
<input type="checkbox" [ngModel]="group.get('status').value=='A'"
(ngModelChange)="group.get('status').setValue($event?'A':'I')"
[ngModelOptions]="{standalone:true}">status
<input formControlName="action">
</div>
</div>
</form>
See that you use an input "ngModel" to control the "check" and a input with formControlName to control the name
You can be an example of all this in stackblitz
const value = this.form.get('status').value ? 'A' : 'I';?