Scala 槽點 - require

require

def this(name: String, age: Int) = {
  this()
  require(name != null && !name.isEmpty, "name")
  require(age > 0, "illegal age")
  Preconditions.checkArgument(name != null && !name.isEmpty, "name required")  // 使用 guava 工具類，這行編譯不過... 改寫爲下兩種調用方式可經過
// Preconditions.checkArgument(name != null && !name.isEmpty, "name required".asInstanceOf[Any])  
// Preconditions.checkArgument(name != null && !name.isEmpty, "name required", null)
  setAge(age)
  setName(name)
}

什麼鬼

1. require
   • 函數簽名: final def require(requirement: Boolean, message: => Any) ，注意第二個參數類型是一個函數
   • 以上栗子中調用了兩次 require 函數，生成兩個匿名對象...
2. ambiguous reference to overloaded definition
   • 編譯錯誤信息：
     Error:(44, 21) ambiguous reference to overloaded definition, both method checkArgument in object Preconditions of type (x$1: Boolean, x$2: String, x$3: Object*)Unit and method checkArgument in object Preconditions of type (x$1: Boolean, x$2: Any)Unit match argument types (Boolean,String) Preconditions.checkArgument(name != null && !name.isEmpty, "name required")