Handing Case Class Exceptions and Compiling them - scala

Question

I am trying to get these two classes to link up.
PatientMonitorExceptions.scala
abstract class PatientMonitorExceptions extends Exception
case class InvalidHeartRate (str:String) extends PatientMonitorExceptions
Here is my main.scala that I am trying to compile with the following line:
main.scala
import gasguru.patient.PatientMonitor
import gasguru.patient.Patient
import gasguru.patient.exceptions.InvalidHeartRate
object Main extends App {
val p = new Patient("snyder","brad");
val v = p.vitalSigns
val pm = new PatientMonitor(p);
p.vitalSigns.heartRate = 160;
println("The patient's heart rate is: " + p.vitalSigns.heartRate + " bpm");
try { pm checkHeartRate v.heartRate
}
catch {
case InvalidHeartRate(x) => println(x);
case _ => println("Something else");
}
}
I am running: scala main.scala to compile this
error: error while loading InvalidHeartRate, Missing dependency 'class InvalidHeartRate', required by ./gasguru/patient/exceptions/InvalidHeartRate.class
What does this error message mean?

Answer 1

When main.scala references InvalidHeartRate, it is referring to the companion object created for your case class InvalidHeartRate, and invoking the unapply method on it to do the match. The InvalidHeartRate object is dependent on the InvalidHeartRate case class being in the classpath. The error message occurred because even though the companion object's .class file (InvalidHeartRate$.class) could be found, the .class file for the case class itself is missing (InvalidHeartRate.class). I would suggest deleting all your .class files and recompiling.