Scala生成的代码工件
示例
的case改性剂引起Scala编译器自动生成的类共同样板代码。手动执行此代码很繁琐，而且会导致错误。以下案例类定义：
case class Person(name: String, age: Int)
...将自动生成以下代码：
class Person(val name: String, val age: Int)
extends Product with Serializable
{
def copy(name: String = this.name, age: Int = this.age): Person =
new Person(name, age)
def productArity: Int = 2
def productElement(i: Int): Any = i match {
case 0 => name
case 1 => age
case _ => throw new IndexOutOfBoundsException(i.toString)
}
def productIterator: Iterator[Any] =
scala.runtime.ScalaRunTime.typedProductIterator(this)
def productPrefix: String = "Person"
def canEqual(obj: Any): Boolean = obj.isInstanceOf[Person]
override def hashCode(): Int = scala.runtime.ScalaRunTime._hashCode(this)
override def equals(obj: Any): Boolean = this.eq(obj) || obj match {
case that: Person =>this.name==that.name&&this.age== that.age
case _ => false
}
override def toString: String =
scala.runtime.ScalaRunTime._toString(this)
}所述case改性剂还产生一个同伴对象：
object Person extends AbstractFunction2[String, Int, Person] with Serializable {
def apply(name: String, age: Int): Person = new Person(name, age)
def unapply(p: Person): Option[(String, Int)] =
if(p == null) None else Some((p.name, p.age))
}应用于时object，case修饰符具有相似的效果（尽管不那么引人注目）。这里的主要收益是toString实现和在hashCode各个过程中保持一致的值。请注意，案例对象（正确）使用引用相等：
object Foo extends Product with Serializable {
def productArity: Int = 0
def productIterator: Iterator[Any] =
scala.runtime.ScalaRunTime.typedProductIterator(this)
def productElement(i: Int): Any =
throw new IndexOutOfBoundsException(i.toString)
def productPrefix: String = "Foo"
def canEqual(obj: Any): Boolean = obj.isInstanceOf[this.type]
override def hashCode(): Int = 70822 // "Foo".hashCode()
override def toString: String = "Foo"
}仍然可以手动实现方法，否则该方法将由case类本身及其伴随对象中的修饰符提供。