I'm a bit stuck with implicit parameters of anonymous functions. Hope somebody'll point me the right direction. Here is what I have. Two files: Main.scala
and Foo.scala
:
// Foo.scala
trait Fun[-A, +B] extends (A => B)
trait ImplicitString[+B] {
def withString(block: String => B)(implicit s: String): B = block(s)
}
object FooFun extends Fun[String, String] with ImplicitString[String] {
def apply(x: String): String = withString { implicit s =>
x + s
}
}
And
// Main.scala
object Main extends App {
implicit val s = "it works!"
println(FooFun("Test:"))
}
I'm expecting to see Test: it works!
printed. But I got a compilation error:
$ scalac Main.scala Service.scala
Service.scala:8: error: could not find implicit value for parameter s: String
def apply(x: String): String = withString { implicit s =>
^
one error found
Am I missing something?
UPDATE :
Looks like I should have imported my implicit val like this:
// Foo.scala
import Main._
...
This works fine.
If you are going to use s
directly inside function, there's no point of marking it as implicit.
You can fix this in this way,
object FooFun extends Fun[String, String] with ImplicitString[String] {
def apply(x: String)(implicit s1:String): String = withString { s =>
x + s
}
}
The problem is, implicit val s
is not visible to the apply method body of FooFun
.
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