CODEWITHSUNDEEP
scalagenericspartialfunction
cdmckay
cdmckay

Reputation: 32290

How to partially apply case class with type parameter in Scala

So I have a tuple that I want to pass as the parameters for a case class in Scala. For case classes without type parameters, this is easy, as I can do:

 scala> case class Foo(a: Int, b: Int)
 defined class Foo

 scala> (Foo.apply _)
 res0: (Int, Int) => Foo = <function2>

 scala> val tuple = (1, 2)
 tuple: (Int, Int) = (1,2)

 scala> res0.tupled(tuple)
 res1: Foo = Foo(1,2)

 scala> Foo.tupled(tuple)
 res2: Foo = Foo(1,2)

However, if the case class has a type parameter, it doesn't seem to work:

scala> (Bar.apply _)
res26: (Nothing, Nothing) => Bar[Nothing] = <function2>

scala> res26.tupled(tuple)
<console>:18: error: type mismatch;
 found   : (Int, Int)
 required: (Nothing, Nothing)
              res26.tupled(tuple)
                           ^
scala> (Bar[Int].apply _)
<console>:16: error: missing arguments for method apply in object Bar;
follow this method with `_' if you want to treat it as a partially applied function
              (Bar[Int].apply _)

scala> Bar.tupled(tuple)
<console>:17: error: value tupled is not a member of object Bar
              Bar.tupled(tuple)
                  ^

scala> Bar[Int].tupled(tuple)
<console>:17: error: missing arguments for method apply in object Bar;
follow this method with `_' if you want to treat it as a partially applied function
              Bar[Int].tupled(tuple)
                 ^

How do I partially apply a case class with a type parameter? I'm using Scala 2.10.3.

Upvotes: 2

Views: 1731

Answers (1)

Urban Vagabond
Urban Vagabond

Reputation: 7732

This appears to work:

scala> case class Foo[X](a:X, b: X)
defined class Foo

scala> Foo.apply[Int] _
res1: (Int, Int) => Foo[Int] = <function2>

scala>

Upvotes: 4

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