Scala Case Class equals implementation
Given the following the classes:
trait ModelWithId {
var id: Long = 0
}
case class EntityAttribute (
val entityId: UUID,
val attrName: String,
val stringVal: Option[String],
val boolVal: Option[Boolean],
val longVal: Option[Long],
val doubleVal: Option[Double],
val byteVal: Option[Array[Byte]]) extends ModelWithId{
override def toString() : String = {
"EntityAttribute(" + entityId.hashCode + "," + attrName.hashCode + "," +
stringVal.map{_.hashCode}.getOrElse(None) + "," + stringVal.hashCode+ "," +
boolVal.map{_.hashCode}.getOrElse(None) + "," + boolVal.hashCode+ "," +
longVal.map{_.hashCode}.getOrElse(None) + "," + longVal.hashCode+ "," +
doubleVal.map{_.hashCode}.getOrElse(None) + "," + doubleVal.hashCode+ "," +
byteVal.map{_.hashCode}.getOrElse(None) + ")"
}
}
And the following comparison functions:
val newAtttributes : List[EntityAttribute]
val withoutIds : List[EntityAttribute]
println("without: " + withoutIds)
println("new: " + newAtttributes)
val differences = newAtttributes.diff(withoutIds)
println("diff: " + differences)
if(newAtttributes.size == 1 && withoutIds.size == 1){
println("==: " + (newAtttributes.get(0) == withoutIds.get(0)))
println("equals: " + (newAtttributes.get(0).equals(withoutIds.get(0))))
println("hequals: " + (newAtttributes.get(0).hashCode == withoutIds.get(0).hashCode))
}
I get the expected difference output 99 out 100 times. Very occasionally the diff function will return an empty list when it should a list of one.
Example:
without: List(EntityAttribute(428861607,-1147340381,None,120224,None,120224,56,-356863126,None,120224,None))
new: List(EntityAttribute(428861607,-1147340381,None,120224,None,120224,23,424930523,None,120224,None))
diff: List()
==: false
equals: false
hequals: false
I can reliably reproduce this error usually after around 10-18 iterations. The two lists are coming from different sources, so they are being constructed differently. I am guessing that it has something to do with auto-boxing开发者_JS百科 or a bad hashCode implementation but I have been bashing my head into a wall for 2 days without progress.
I'm using scala 2.9.0-1.
Those two EntityAttribute
's contain different values for longVal
. The default equals
implementation for case classes takes all members into account, so that makes them unequal. If you want to only use a subset of the members you should define your own equals
and hashCode
.
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