notEquals static method
Checks that checkValue does not equal compareValue.
Attempts to compare checkValue and compareValue. If they are equal than
errorMessage is returned if provided, or the default error if not.
Otherwise null is returned
Implementation
static String? notEquals(String? checkValue, String compareValue,
{String? errorMessage}) {
if (checkValue == compareValue) {
return errorMessage ?? "Field does equals '$compareValue'";
}
return null;
}