Scala 2.10的枚举和映射 [英] Enumeration and mapping with Scala 2.10

问题描述

我正在将我的应用程序移植到Scala 2.10.0-M2。我看到一些很好的改进，更好的警告从编译器。但是我也有一些错误，所有这些都与我有关，从 Enumeration.values 映射。

我会给你是一个简单的例子。我想有一个枚举，然后预先创建一堆对象，并构建一个使用枚举值作为键，然后一些匹配对象作为值的映射。例如：

 对象短语扩展枚举{
 type Phrase = Value 
 val PHRASE1 = Value（我的短语1）
 val PHRASE2 =值（我的短语2）
} 
 
类实体（文本：字符串）
 
对象测试{
 val myMapWithPhrases = Phrase.values.map（p =>（p  - > new Entity（p.toString）））toMap 
} 
  

现在这个在Scala 2.8和2.9上工作得很好。但是2.10.0-M2给了我以下警告：

  [ERROR] common / Test.scala：21：error：diverged implicit扩展类型scala.collection.generic.CanBuildFrom [common.Phrase.ValueSet，（common.Phrase.Value，common.Entity），那] 
 [INFO]以方法newCanBuildFrom开头的对象SortedSet 
 [ INFO] val myMapWithPhrases = Phrase.values.map（p =>（p  - > new Entity（p.toString）））。toMap 
 ^ 
  
解决方案
 p $ p 
 
 
它基本上是一个类型不匹配的错误。您可以通过首先转换为列表来解决问题：
  scala> Phrase.values.toList.map（p =>（p，new Entity（p.toString）））。toMap 
 res15：scala.collection.immutable.Map [Phrase.Value，Entity] = Map（My短语1  - > Entity @ d0e999，我的短语2  - > Entity @ 1987acd）
  
信息，请参阅什么是分歧隐式扩展scalac消息的答案？和什么是分歧的隐式扩展错误？ 
 
I'm trying to port my application to Scala 2.10.0-M2. I'm seeing some nice improvements with better warnings from compiler. But I also got bunch of errors, all related to me mapping from Enumeration.values.

I'll give you a simple example. I'd like to have an enumeration and then pre-create bunch of objects and build a map that uses enumeration values as keys and then some matching objects as values. For example:
object Phrase extends Enumeration {
  type Phrase = Value
  val PHRASE1 = Value("My phrase 1")
  val PHRASE2 = Value("My phrase 2")
}

class Entity(text:String)

object Test {
    val myMapWithPhrases = Phrase.values.map(p => (p -> new Entity(p.toString))).toMap  
}
Now this used to work just fine on Scala 2.8 and 2.9. But 2.10.0-M2 gives me following warning:
[ERROR] common/Test.scala:21: error: diverging implicit expansion for type scala.collection.generic.CanBuildFrom[common.Phrase.ValueSet,(common.Phrase.Value, common.Entity),That]
[INFO] starting with method newCanBuildFrom in object SortedSet
[INFO]   val myMapWithPhrases = Phrase.values.map(p => (p -> new Entity(p.toString))).toMap
                                                 ^
What's causing this and how do you fix it?
解决方案
It's basically a type mismatch error. You can work around it by first converting is to a list:
scala> Phrase.values.toList.map(p => (p, new Entity(p.toString))).toMap
res15: scala.collection.immutable.Map[Phrase.Value,Entity] = Map(My phrase 1 -> Entity@d0e999, My phrase 2 -> Entity@1987acd)
For more information, see the answers to What's a "diverging implicit expansion" scalac message mean? and What is a diverging implicit expansion error?

                        
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