How to call a generic method with an anonymous type involving generics?
- by Alex Black
I've got this code that works:
def testTypeSpecialization = {
class Foo[T]
def add[T](obj: Foo[T]): Foo[T] = obj
def addInt[X <% Foo[Int]](obj: X): X = {
add(obj)
obj
}
val foo = addInt(new Foo[Int] {
def someMethod: String = "Hello world"
})
assert(true)
}
But, I'd like to write it like this:
def testTypeSpecialization = {
class Foo[T]
def add[X, T <% Foo[X](obj: T): T = obj
val foo = add(new Foo[Int] {
def someMethod: String = "Hello world"
})
assert(true)
}
This second one fails to compile:
no implicit argument matching parameter type (Foo[Int]{ ... }) = Foo[Nothing] was found.
Basically:
I'd like to create a new anonymous
class/instance on the fly (e.g. new
Foo[Int] { ... } ), and pass it into
an "add" method which will add it to
a list, and then return it
The key thing here is that the
variable from "val foo = " I'd like
its type to be the anonymous class,
not Foo[Int], since it adds methods
(someMethod in this example)
Any ideas?
I think the 2nd one fails because the type Int is being erased. I can apparently 'hint' the compiler like this:
def testTypeSpecialization = {
class Foo[T]
def add[X, T <% Foo[X]](dummy: X, obj: T): T = obj
val foo = add(2, new Foo[Int] {
def someMethod: String = "Hello world"
})
assert(true)
}
