@FunctionalInterface VS @JsFunction

[Jan Blok]

Hi,

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

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 

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

Regards Jan 

[Thomas Broyer]

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. 

[Jan Blok]

Yeah sure, there are many workarounds...which leads to bloat as shown.

Then my request would be to by default have Runnable and Callable in gwt java emulation to be attributed by default with interop.JsFunction :-)

Regards Jan

[Thomas Broyer]

Which is not possible due to the many contraints of JsFunction, that would break a whole lot of apps.