前向引用扩展了值的定义问题

Question

我在scala中解决隐式值有一些问题，并且我在netbeans中有神秘的错误信息:

"error:前向引用扩展了值的定义…"

或者在scala控制台中，我有另一个错误消息

"type mistmatch:29: error: type mismatch;发现:工厂。需要的类型(具有底层类型对象工厂):GenericFactory "

我的类和主函数的一些描述:

import java.util.Random
//////////
// Main //
//Implicit random for all classes and object
implicit val aprng = new Random
//Implicit object Factory used in other class
implicit val factory = Factory
abstract class GenericFactory {
def build 
}
object Factory extends GenericFactory{
def build = println("return factory")
}
class A (rate: Random => Double = aprng => aprng.nextFloat, val factory : GenericFactory) {
  def this(rate : Double, factory : GenericFactory) = this( _ => rate, factory)
  def operate(genomes: IndexedSeq[Int])(implicit aprng: Random) = { 
println("calculate genomes with aprng random values")}
}
object B{
val instanceOfA = new A(rate => 0.5d,factory)
}

我有两个问题，因为1)我可以在类A的参数传递对象，所以我定义了一个抽象类来传递这个抽象类，但这在这里不起作用:/2)之后，我定义到A类的隐式值不能被识别，并失败，并显示错误信息。

你有解决这个问题的想法或答案吗?

编辑1

我在agsteel的帮助下更新了代码，没关系，代码正在运行:)

import java.util.Random
//////////
// Main //
//Implicit random for all classes and object
implicit val aprng = new Random
implicit val function: Random => Double = arpng => arpng.nextFloat
abstract class GenericFactory 
{
  def build = println("build")
}
implicit object Factory extends GenericFactory
{
  def build = println("return factory")
}
class A (implicit rate: Random => Double, implicit val factory : GenericFactory) {
  //def this(rate : Double, factory : GenericFactory) = this( _ => rate, factory)
  def operate(genomes: IndexedSeq[Int])(implicit aprng: Random) = { 
    println("calculate genomes with aprng random values")}
}
object B{
val instanceOfA = new A
}

Answer 1

我不知道你在这里想达到什么目的，但这里有一些建议:

1)代替:

implicit val factory = Factory
object Factory extends GenericFactory { ...

试试这个:

implicit object Factory extends GenericFactory { ...

2)据我所知，lambda的默认值只能通过隐式提供，因此，而不是:

class A (rate: Random => Double = aprng => aprng.nextFloat, ...

试试这个:

implicit val function: Random => Double = arpng => arpng.nextFloat
class A (implicit rate: Random => Double) ( ...