Difference between case class and case object?

Question

I am learning Scala and Akka and in my recent lookup for a solution, I found something like

 case class TotalTaxResult(taxAmount:Double)
 case object TaxCalcul         


        

Answer 1

A case object is a singleton case class. They are used kind of like enumeration values. It can be used in pattern matching just like any other value:

TaxCalculationTimeout match {
  case TaxCalculationTimeout => println("hello")
}

When you define a case class, you are creating a template for instances of that class. TotalTaxResult(1.0) and TotalTaxResult(2.0) are two different values of the same type. Whereas there is exactly one TaxCalculationTimeout value.