错误：（63，3）类型不匹配；找到：所需单位：双

Question

val Match: (String) => Double = (address: String) => {
    val address =
    if (address == null)
      empty
    else
      Address
}

在此代码中，我遇到此错误

  

    

类型不匹配；找到：所需单位：双倍

  

Answer 1

Match函数的返回类型是一个接受string并返回double的函数

(String) => Double

您在评论中提到

  

    

val空= 0.2，val地址= 0.0

  

因此正确的函数定义应为

val Match: (String) => Double = (address: String) => {
   if (address == null)
      empty
    else
      Address
}

错误是因为您没有从i f else表达式中计算出的函数中返回双精度值，并且在范围内使用了与输入参数相同的变量名函数val address =

或者，您也可以使用赋值并返回该赋值

val Match: (String) => Double = (address: String) => {
   val addr = if (address == null)
      empty
    else
      Address
  addr
}

我希望答案会有所帮助

Answer 2

或者，

val empty = 0.2; val Address = 0.0

val Match: (String) => Double =
 (address:String)=>address match{
 case null => empty
 case _ => Address
 }

在Scala REPL中：

scala> Match(null)
res79: Double = 0.2

scala> Match("")
res80: Double = 0.0

scala> Match("yoohh")
res81: Double = 0.0