Re: @FunctionalInterface VS @JsFunction

On Monday, January 15, 2018 at 4:03:11 PM UTC+1, Jan Blok wrote:

Hi,

Would it be possible for GWTc to handle java.lang.FunctionalInterface as if it was jsinterop.annotations.JsFunction ?

No, if only because JsFunction has many constraints: http://www.gwtproject.org/javadoc/latest/jsinterop/annotations/JsFunction.html

 

The reason for asking is, I have this java code:

    public void transaction(Runnable runnable) {

        startTransaction();

        try {

            runnable.run();

        }

        finally {

            endTransaction();

        }

    }

when I expose this method via jsinterop I get a warning "not usable from javascript"

I intent to use it from JS/TS as: myJavaLib.transaction(() => doSomethingInTransaction(...));

but this is not possible unless I supersource java.lang.Runnable and add @JsFunction 

You'd need to create an overload taking a JsFunction as input, and exposing that one.

@JsFunction @FunctionalInterface
interface TransactionCallback {
  void run();
}


@JsMethod
public void transaction(TransactionCallback callback) {
  startTransaction();
  try {
    callback.run();
  } finally {
    endTransaction();
  }
}

// Note: not a @JsMethod
public void transaction(Runnable runnable) {
  transaction((TransactionCallback) runnable::run);
}

 

It seems to me that @FunctionalInterface and @JsFunction are very similar already...

And this is why the javadoc for JsFunction recommends also annotating the interface with FunctionalInterface. 

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