如何复制案例类对象？

Question

这是我曾尝试

sealed abstract class Tree 
case class NewNode(left: Tree,center: Tree, right: Tree) extends Tree 

我只是想复制整个对象

scala> val treeM = treeD.copy_ 
<console>:16: error: value copy_ is not a member of NewNode 
     val treeM = treeD.copy_ 
        ^

以上不工作

scala> val treeM = treeD.copy(_,_,_) 
treeM: (Tree, Tree, Tree) => NewNode = <function3> 

scala> println("Tree M == Tree D: %s" format (treeM == treeD).toString) 
<console>:18: warning: (Tree, Tree, Tree) => NewNode and NewNode are unrelated: they will most likely never compare equal 
     println("Tree M == Tree D: %s" format (treeM == treeD).toString) 

如何编写正确的对象副本？

Answer 1

拨打电话copy没有任何参数。

val treeM = treeD.copy() 

Answer 2

你可以，但没有理由复制不可变对象。