Custom Validator Control Quantity in Reactive Forms

Question

I had a hard time implementing a custom validation in my reactive forms in Angular. I need to control the quantity. The quantity should not be more than the available quanti

Answer 1

the key is using "parent" to reach the formArray. then we can use map to transform the array and get only que quantity and reduce to get the sum of the quantities

customValidator(campo1: string) {
    return (group: FormGroup): { [key: string]: any } => {
      //get the formArray
      const form=(group.parent as FormArray);
      if (form)
      {
        //get the available quantity using parent
        let available =form.parent.get('available_quantity').value;

        //the final available are the available less each quantity
        available=form.value //In form.value we have e.g. [{quantity:10..},{quantity:16}]
          .map(x=>x.quantity?+x.quantity:0)  //using map we have, e.g. [10,16]
          .reduce((a, b) => a - b, available)  //using reduce we substract the quantities to available
        if (available<0) {
          return {
            out: true
          };
        }
      }
    }
  }