Case class equality is based solely on its primary constructor attributes, whether they're var
or val
(yes, you can make them var
by giving an explicit var
to override the implied val
that case class constructor args possess.) Adding properties in the body of a case class
does not influence the compiler-generated equals(other: Any)
method.
Witness:
package rrs.scribble
object CCVarEq
{
case class CC1(i: Int, j: Float, var k: Double)
case class CC2(i: Int, j: Float, var k: Double) {
var l = math.Pi
}
def show {
val cc11 = CC1(1, 2.0f, 3.0)
val cc12 = CC1(1, 2.0f, 3.0)
val cc21 = CC2(1, 2.0f, 3.0); cc21.l = math.E
val cc22 = CC2(1, 2.0f, 3.0)
printf("cc11 == cc12: %s%n", cc11 == cc12); cc12.k = math.Pi * math.E
printf("cc11 == cc12: %s%n", cc11 == cc12)
printf("cc21 == cc22: %s%n", cc21 == cc22)
}
}
In the REPL:
scala> import rrs.scribble.CCVarEq._
import rrs.scribble.CCVarEq._
scala> show
cc11 == cc12: true
cc11 == cc12: false
cc21 == cc22: true
And all jamie's points about concurrency are valid, too.