Is this possible to get:
object test[A](l: Int): List[A] = {
...
}
You know what i mean. Is that possible?
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2 Answers
Maybe you mean something like
object MyListMaker {
def test[A](a0: A, n: Int): List[A] = (1 to n).map(_ => a0).toList
}
scala> MyListMaker.test("Fish",7)
res0: List[java.lang.String] = List(Fish, Fish, Fish, Fish, Fish, Fish, Fish)
Only one copy of an object exists; if you want to create a method that does something generic, add the type parameter to the method (not the object).
2 Comments
Daniel C. Sobral
You should have made the method
apply instead of test, which would give a much closer syntax to what was asked.
Rex Kerr
@Daniel - Maybe so. I had trouble figuring out what was being asked, and using
apply adds an extra wrinkle in understanding why it works. But, yes, with def apply... it would just be MyListMaker("Fish",7). I was more worried about making a list of As without actually having any A's.Traits or Objects cannot have constructor parameters, and objects cannot have type parameters.
An object is effectively a singleton instance of a class. Therefore you can't have a generic definition of it, because it has only one name.
Your best option is to define a method within an object which returns the list you want.
3 Comments
matiit
So what would be the best way for generating List of some type?
Randall Schulz
Traits certainly may have type parameters! Objects may not.
Matthew Farwell
To clarify: traits can have type parameters, but not constructor parameters. Answer edited