CODEWITHSUNDEEP
scala
Vishal John
Vishal John

Reputation: 4382

Equality of a list of classes

I am trying to compare two Lists containing case classes. Can't figure out which method to override to get this working. Please refer to the code below.

trait Filter {
  def toQueryString: String
}
trait SimpleFilter extends Filter {
  val key: String
  val value: Any

  override def toQueryString = value match {
    case v: String => s"$key='$v'"
    case _         => s"$key=$value"
  }
  override def toString = "$key:$value"

  override def equals(that: Any) = {
    that match {
      case s: SimpleFilter => {
        key == key && value == value
      }
      case _ => false
    }
  }
  override def hashCode() = key.hashCode + value.hashCode
}

class DestinationFilter(override val value: String) extends SimpleFilter {
  override val key = "destination"
}
object DestinationFilter {
  def apply(value: String) = new DestinationFilter(value)
}

object Tester {

  def main(args: Array[String]): Unit = {
    val d1 = DestinationFilter("Google")
    val d2 = DestinationFilter("Google")
    val l1 = List(d1)
    val l2 = List(d2)
    println(11 == 12)
    println(d1 == d2)
  }

}

which returns

false
true

Can't understand why the list comparison returns false. Ultimately what I want is this to be equal

List(DestinationFilter("Amazon"), LocationFilter("Yahoo"), DestinationFilter("Google") == List(DestinationFilter("Yahoo"), LocationFilter("Amazon"), DestinationFilter("Google")

*they should be equal irrespective of order.

Upvotes: 0

Views: 58

Answers (1)

Noah
Noah

Reputation: 13959

You have a typo in your comparison, 11 and 12 should be l1 and l2:

println(l1 == l2) // true

So 11 == 12 is always false, you're just comparing Ints.

You also need to change your equals override, your just comparing key and value to themselves, which is always true:

  override def equals(that: Any) = {
      that match {
        case s: SimpleFilter =>
          key == s.key && value == s.value //edited
        case _ => false
      }
    }

Upvotes: 1

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