Question

My implementation of a getHandler method, which is defined on a Java interface, has failed, and I don’t know why. Here is the method signature:

<H extends EventHandler> H getHandler( Type<H> type, int index );

My implementation in Scala is:

def getHandler[H <: com.google.gwt.event.shared.EventHandler]
    (aType: Type[H], index: Int): H 
    = new com.google.gwt.event.shared.EventHandler() {}

…but the compiler gives me this message:

type mismatch;  
    found: java.lang.Object with com.google.gwt.event.shared.EventHandler
    required: H

Where have I erred?

Answer 1

I think this may make it compile:

def getHandler[H <: com.google.gwt.event.shared.EventHandler]
    (aType: Type[H], index: Int): H = {
  val h = new com.google.gwt.event.shared.EventHandler() {}
  h.asInstanceOf[H]
}

It’s expecting an H. As Lachlan says, aType probably is needed somewhere.