Scala - 使用toMap时发散隐式扩展

Question

I have the following definition of an enum:

object GraphType extends Enumeration {
  type Type = Value
  val MESSAGE, REQUEST, ERRORS = Value
}

Now I am trying to map each of the type to the corresponding, new TimeSeries as follows:

val dataSets = ( GraphType.values map (graphType => graphType -> new TimeSeries(graphType)) ).toMap

the type system lists datasets as Map[GraphType.Value, TimeSeries] which is precisely what I want. However, compilation fails with error message:

error: diverging implicit expansion for type scala.collection.generic.CanBuildFrom[ird.replay.gui.GraphType.ValueSet,(ird.replay.gui.GraphType.Value, org.jfree.data.time.TimeSeries),That]
starting with method newCanBuildFrom in object SortedSet
val dataSets = GraphType.values map (graphType => graphType -> new TimeSeries(graphType)) toMap

COuld anyone provide some explanation for this, rather cryptic, error message? Thanks

Answer 1

Try converting the Set of values for the enum to a List first like so:

val dataSets = (GraphType.values.toList.map(gt => (gt, new TimeSeries(gt)))).toMap

Something about that being a Set did not agree with how you were attempting to convert it to a Map , but it seems to work just fine with a List