How to compare attribute values from different classes?

问题

I've two classes with a few attributes that have the same names, for example:

case class Rect(x: Int, y: Int)
case class Squa(x: Int, y: Int)

To compare it I do:

val r = new Rect(2, 2)
val s = new Squa(2, 2)

r.x == s.x && r.y == x.y

If I have "N" attributes I have to compare one by one, is there a way to compare all attributes at once since they have the same name? I've tried:

r.asInstanceOf[Squa] eq s

But this gives me the error:

class Rect cannot be cast to class Squa (Rect and Squa are in unnamed module of loader scala.reflect.internal.util.ScalaClassLoader$URLClassLoader @3b81a1bc)

The running example: https://repl.it/join/eegmixii-rafa_acioly

回答1:

You can use productIterator. For example you can do:

r.productIterator.sameElements(s.productIterator)

Code run can be found at Scastie

Another option you have is to share a trait between the 2. Let's define:

trait Base extends Ordered[Base] {
  val x: Int
  val y: Int

  override def compare(that: Base): Int = {
    if (x != that.x) {
      x - that.x
    } else {
      y - that.y
    }
  }
}

Then we can test it with:

println("Rect(2,2).compareTo(Squa(2,2)): " + Rect(2,2).compareTo(Squa(2,2))) // 0
println("Rect(2,2) > Squa(2,2) " + (Rect(2,2) > Squa(2,2))) // false
println("Rect(2,2) >= Squa(2,2) " + (Rect(2,2) >= Squa(2,2))) // true
println("Rect(3,2) >= Squa(2,2) " + (Rect(3,2) >= Squa(2,2))) // true
println("Rect(3,2) >= Squa(2,3) " + (Rect(3,2) >= Squa(2,3))) // true
println("Rect(2,3) >= Squa(3,2) " + (Rect(2,3) >= Squa(3,2))) // false

Code run can be found at Scastie.

来源：https://stackoverflow.com/questions/64573743/how-to-compare-attribute-values-from-different-classes

标签

scala