Scala 槽点

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 工具类，这行编译不过... 改写为下两种调用方式可通过
// Preconditions.checkArgument(name != null && !name.isEmpty, "name required".asInstanceOf[Any])  
// Preconditions.checkArgument(name != null && !name.isEmpty, "name required", null)
  setAge(age)
  setName(name)
}

什么鬼

1. require

   • 函数签名: final def require(requirement: Boolean, message: => Any) ，注意第二个参数类型是一个函数
   • 以上栗子中调用了两次 require 函数，生成两个匿名对象...

2. ambiguous reference to overloaded definition

   • 编译错误信息：

     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")