Scala Library
scala.util

trait Hashable
[source: scala/util/Hashable.scala]
trait Hashable
extends AnyRef

A convenience trait for simplifying hashCode creation. Mix this into a class and define val hashValues = Seq(x1, x2, ...) and your hashCode will be derived from those values. If you define equals in terms of equalHashValues then your hashCode and equals methods will never be out of sync. Something like: 

    override def equals(other: Any) = other match {
      case x: YourClass => this equalHashValues x
      case _            => false
    }
Author
Paul Phillips
Direct Known Subclasses:
StrictHashable
Method Summary
protected def equalHashValues (other : Any) : Boolean
override def hashCode : Int
Returns a hash code value for the object.
protected def hashSeed : Int
protected abstract def hashValues : Seq[Any]
Methods inherited from AnyRef
getClass, equals, clone, toString, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized
Methods inherited from Any
==, !=, isInstanceOf, asInstanceOf
Method Details
protected abstract def hashValues : Seq[Any]
protected def hashSeed : Int
override def hashCode : Int
Returns a hash code value for the object.

The default hashing algorithm is platform dependent. Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0. However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the equals method.

Returns
the hash code value for the object.

protected def equalHashValues(other : Any) : Boolean
Scala Library