Question

Suppose a class defines an implicit function that converts an integer to a String:

class Dollar() {
  implicit def currency(num: Int): String = "$" + num.toString

  def apply(body: => Unit) {
    body
  }
}

and we also have a function that prints a number transformed by the implicit function:

def printAmount(num: Int)(implicit currency: Int => String) {
  println(currency(num))
}

then we can call the method printAmount() in the constructor of the class Dollar:

val dollar = new Dollar {
  printAmount(32) // prints "$32"
}

However, if we want to provide the implicit function for a code block, a compilation error occurs because the implicit value does not applied:

dollar {
  printAmount(14) // Error: No implicit view available from Int => String
}

As I know, Groovy has a keyword use for the case like this. Is there any way to provide implicit functions for a certain code block in Scala?

Answer 1

You can change dollar such that it takes a function from a conversion function to Unit.

dollar(f:(Int => String) => Unit) = {
  //...
}

Then you can use dollar like this:

dollar ( implicit conversion => {
  printAmount(14)
})