Custom validation for positive numbers

Question

I was trying to find the information, if there are any built-in validators, that check if the input is a positive number?

I was trying to build the following:

static nonZero(control:Control) {
    if (Number(control.value) < 0) {
        control.setErrors({nonZero: true})
    } else {
    control.setErrors(null)
    }
}

However, I didn't know how to use it in my form builder:

this.form = _formBuilder.group({
            field:['', Validators.required]})

What am I doing wrong?

Answer 1

You can configure it this way by leveraging the Validators.compose method:

this.form = _formBuilder.group({
        field:['', Validators.compose([
                     Validators.required, nonZero ])
        ]});

This allows you to define your two synchronous validators for the field.

Edit

I would implement the validator this way:

static nonZero(control:Control):{ [key: string]: any; } {
  if (Number(control.value) < 0) {
    return {nonZero: true};
  } else {
    return null;
  }
}