How can I take any function as input for my Scala wrapper method?

Let's say I want to make a little wrapper along the lines of:

def wrapper(f: (Any) => Any): A开发者_如何学JAVAny = {
  println("Executing now")
  val res = f
  println("Execution finished")
  res
}

wrapper {
  println("2")
}

Does this make sense? My wrapper method is obviously wrong, but I think the spirit of what I want to do is possible. Am I right in thinking so? If so, what's the solution? Thanks!

If you want your wrapper method to execute the wrapped method inside itself, you should change the parameter to be 'by name'. This uses the syntax => ResultType.

def wrapper(f: => Any): Any = {
  println("Executing now")
  val res = f
  println("Execution finished")
  res
}

You can now do this,

wrapper {
  println("2")
}

and it will print

Executing now
2
Execution finished

If you want to be able to use the return type of the wrapped function, you can make your method generic:

def wrapper[T](f: => T): T = {
  println("Executing now")
  val res: T = f
  println("Execution finished")
  res
}

In your case you are already executing the function println and then pass the result to your wrapper while it is expecting a function with one arguments (Any) and that return Any.

Not sure if this answer to your question but you can use a generic type parameter and accept a function with no arguments that return that type:

def wrapper[T](f: () => T) = {
  println("Executing now")
  val res = f() // call the function
  println("Execution finished")
  res
}

wrapper {
  ()=>println("2") // create an anonymous function that will be called
}