Question

你能帮我理解行为吗

  //Creating a tuple
  val myTuple = ("Sudipta","Deb","Switzerland",1234)
                                                  //> myTuple  : (String, String, String, Int) = (Sudipta,Deb,Switzerland,1234)
  myTuple._2                                      //> res0: String = Deb
  myTuple._4                                      //> res1: Int = 1234
  val (first, second, third, fourth) = myTuple    //> first  : String = Sudipta
                                                  //| second  : String = Deb
                                                  //| third  : String = Switzerland
                                                  //| fourth  : Int = 1234
  //val (first1, second1, _) = myTuple

现在最后一行给了我错误：

constructor cannot be instantiated to expected type;  found   : (T1, T2, T3)  required: (String, String, String, Int)

我的问题是为什么它的表现如此？在Scala for Impatient Book中写道：

You can use a _ if you don’t need all components:
val (first, second, _) = t

仅供您参考，如果您想查看完整代码，它就在我的GitHub存储库中。链接：Scala Worksheet

Answer 1

您必须为每个未使用的元组成员添加一个_。

val (first1, second1, _, _) = myTuple

Scala中的元组没有按预期工作

1 个答案: