问题
I am writing a data structure (basically a hashmap) in Scala that will take one tuple (of possibly different number of arguments each time) and do something with it. To generically implement this, I defined a type:
type T <: Tuple1[_] with Tuple2[_,_] with Tuple3[_,_,_] with Tuple4[_,_,_,_] with Tuple5[_,_,_,_,_]
and then the data structure
val map = new HashMap[Int, T]
But this is ugly, since I have to change the type every time I have to handle more arguments in a tuple. Is there to define a generic tuple type?
Thanks, Y.K.
回答1:
The first solution is to use Product, as said by @om-nom-nom. Indeed, it's the only common supertype of all tuples.
val map = Map.empty[Int, Product]
map + (2 -> ("a", "b"))
And then to use the methods productArity, productElement and productIterator to handle the returned value.
You can also use a map of list (or any indexed collection).
val map = Map.empty[Int, List[_]]
map + (3 -> ("a" :: "b" :: "c" :: Nil))
map + (2 -> List("a", "b"))
The last solution is not that convenient for the user, but at least you know exactly what collection you handle. You could also add an implicit.
来源：https://stackoverflow.com/questions/13786276/scala-generic-tuple-type-with-multiple-subtypes