正向引用延伸到价值问题的界定， [英] Forward reference extends over definition of value problem

问题描述

我在斯卡拉一些问题解决隐含的价值观，和我有NetBeans中神秘的错误消息：

  

错误：正向引用延伸的价值定义...

或阶控制台我有一个其他错误消息

  

型mistmatch：29：错误：类型不匹配;实测值：
  Factory.type（与基础类型的对象厂）要求：
  GenericFactory

我的阶级和主要功能的一些描述：

 导入了java.util.Random//////////
// //主//隐随机的所有类和对象
隐VAL aprng =新的随机在其他类中使用//隐式对象厂
隐VAL厂=厂抽象类GenericFactory {
打造高清
}对象工厂扩展GenericFactory {
高清打造=的println（返回工厂）
}A级（速度：随机=＆GT;双= aprng =＆GT; aprng.nextFloat，VAL工厂：GenericFactory）{  DEF这（速度：双，工厂：GenericFactory）=这（_ =＆GT;月率，工厂）  DEF操作（基因组：IndexedSeq [INT]）（隐含aprng：随机）= {
的println（计算与aprng随机值基因组）}
}对象B {
VAL instanceOfA =新的A（率=＆GT; 0.5D，厂）
}
 

我有2个问题，因为1）我可以在A类的参数传递一个对象，所以我定义一个抽象类，通过这个抽象类，但不能在这里工作：/
2）在此之后，我定义为A类隐含的价值不被认可，并失败，出现错误信息。

你有一个想法或一个答案来解决这个问题呢？

编辑1

我更新code与agisteel的帮助下，它的确定，code运行：）

 导入了java.util.Random//////////
// //主//隐随机的所有类和对象
隐VAL aprng =新的随机
隐Val函数：随机=＆GT;双= arpng =＆GT; arpng.nextFloat抽象类GenericFactory
{
  高清打造=的println（建）
}隐式对象厂延伸GenericFactory
{
  高清打造=的println（返回工厂）
}A类（隐率：随机=＆GT;双，隐VAL工厂：GenericFactory）{  //这个DEF（速度：双，工厂：GenericFactory）=这（_ =＆GT;月率，工厂）  DEF操作（基因组：IndexedSeq [INT]）（隐含aprng：随机）= {
    的println（计算与aprng随机值基因组）}
}对象B {
VAL instanceOfA =新的A
}
 

解决方案

我不知道你正试图在这里实现的目标，但这里有一些提示：

1），而不是：

 隐VAL厂=厂
对象工厂扩展GenericFactory {...
 

试试这个：

 隐式对象延伸厂{GenericFactory ...
 

2）lambda表达式的默认值只能通过implicits尽量提供我所知，所以不是：

  A级（速度：随机=＆GT;双= aprng =＆GT; aprng.nextFloat，...
 

试试这个：

 隐Val函数：随机=＆GT;双= arpng =＆GT; arpng.nextFloat
A类（隐率：随机=＆GT;双人间）（...
 

我希望这个信息是非常有用的。

i have some problem in scala to resolve implicit values, and i have the cryptic error message in netbeans :

"error : Forward reference extends over definition of value ..."

or in the scala console i have an other error message

"type mistmatch :29: error: type mismatch; found : Factory.type (with underlying type object Factory) required: GenericFactory"

Some description of my class and main function :

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)
}

I have 2 problem because 1) i can pass an object in argument of class A, so i define an abstract class to pass this abstract class, but that not work here :/ 2) After that, my implicit value defined into class A is not recognized, and fail with error message.

Do you have an idea or an answer to resolve this problem ?

Edit 1

I update the code with help of agisteel, it's ok, code running :)

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
}

解决方案

I'm not sure what you are trying to achieve here, but here are few tips:

1) instead of:

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

try this:

implicit object Factory extends GenericFactory { ...

2) Default values for lambdas can only be provided via implicits as far as I know, so instead of:

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

try this:

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

I hope this info is useful.

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