Question

Writing out a Scala class and problem here is that the compiler thinks that the code is a unit not returning the proper value. It’s a method used to set a property in the class:

def setObject(`object`:StripeObject):StripeObject = {
    this.`object` = `object`
  }

The error is: type mismatch; found : Unit required: com.stripe.StripeObject

The full class is:

case class EventData(var previousAttributes: HashMap[String,Object], var `object`:StripeObject) extends StripeObject {

  def getPreviousAttributes = {
    previousAttributes
  }

  def setPreviousAttributes(previousAttributes: HashMap[String, Object]) = {
    this.previousAttributes = previousAttributes
  }

  def getObject = {
    `object`
  }

  def setObject(`object`:StripeObject):StripeObject = {
    this.`object` = `object`
  }
}

How do I make sure it doesn’t return a Unit?

Answer 1

In Java setters are usually defined with void return type:

public void setObj(StripeObject name);

The Scala equivalent is Unit, which is also the value of an assignment expression. So in Scala you’d write a setter as one of the following (which are all equivalent, with the first being the most idiomatic):

def setObj(obj: StripeObject) {
  this.obj = obj
}

def setObj(obj: StripeObject): Unit = {
  this.obj = obj
}

def setObj(obj: StripeObject) = this.obj = obj

This is just a convention for setters, though, and you could easily return the value if you wanted:

def setObj(obj: StripeObject): StripeObject = {
  this.obj = obj
  obj
}

This would be a bit unusual, but wouldn’t be likely to cause problems, even for callers who were expecting Unit.