Type matching on generic Scala trait - scala

Question

I am just dipping my toes into generics and am wondering if there is a better way to achieve the following:
I have a sealed trait that has an abstract name and an overridden equals(). I want the overridden equals to match on both type and name. Below is what I have.
sealed trait NamedCampaign[A <: NamedCampaign] {
def name: String
override def equals(obj: Any): Boolean = obj match {
case x: A => x.name == this.name
case _ => false
}
}
case class AdCampaign(name: String, objective: String, status: String, buyingType: String) extends NamedCampaign[AdCampaign]
case class AdSet(name: String, status: String, dailyBudget: Int, lifetimeBudget: Int, startTime: Int, endTime: Int, campaign: String) extends NamedCampaign[AdSet]
In layman's terms, I want two objects to be considered equal if they are the same class and have the same name. Is there a better/faster/more idiomatic way of doing this?

Answer 1

What you have can't work because of erasure. The type A isn't known at runtime.
Adapted from this related answer:
sealed trait NamedCampaign[A <: NamedCampaign] {
implicit def classTagA: ClassTag[A]
def name: String
override def equals(obj: Any): Boolean = obj match {
case classTagA(x) => x.name == this.name
case _ => false
}
}
case class AdCampaign(name: String, objective: String, status: String,
buyingType: String)(implicit val classTagA: ClassTag[AdCampaign])
extends NamedCampaign[AdCampaign]
case class AdSet(name: String, status: String, dailyBudget: Int,
lifetimeBudget: Int, startTime: Int, endTime: Int, campaign: String)
(implicit val classTagA: ClassTag[AdSet]) extends NamedCampaign[AdSet]
A better way to write this is with a canEqual method.
sealed trait NamedCampaign {
def name: String
def canEqual(that: Any): Boolean
override def equals(other: Any): Boolean = other match {
case that: NamedCampaign => (that canEqual this) &&
(this.name == that.name)
case _ => false
}
}
case class AdCampaign(name: String, objective: String, status: String,
buyingType: String) extends NamedCampaign {
override def canEqual(that: Any) = that.isInstanceOf[AdCampaign]
}
case class AdSet(name: String, status: String, dailyBudget: Int,
lifetimeBudget: Int, startTime: Int, endTime: Int, campaign: String)
extends NamedCampaign {
override def canEqual(that: Any) = that.isInstanceOf[AdSet]
}
My two cents: I don't think it's ever appropriate to override equals on a case class. You'll regret it the moment you ever want to compare all of the fields (which you're likely to want to do in, say, a unit test).