[Gwt-openlayers-devl] More suggestions about org.gwtopenmaps.openlayers.client.util.JSObject

[Edwin C. <com...@gm...>]

Hi Ying Xia,

Sorry I misspelled your name on a previous post. I have deleted that post.
Here it is the content again for the developer list:

I have been playing a bit with implemeting one or more invoke methods.

When functions are invoked it is on OpenLayers objects (The
getProperty/setProperty methods are for the config objects, and it's never
necessary to invoke functions on config objects). Often these functions
return values and I think it may get messy to get the return values by their
correct type.

Maybe you have some suggestions when you looking at what I have written
below, since it looks like you were already using code to invoke functions
(or did you create that after seeing getProperty/setProperty?). What did you
do if a function returned a String, floating point number, or integer?
Please read on to see what I mean.

I found that I needed the following to code to invoke toString of Size and
have it return a String (for an easy example and for briefness I made a
variant to invoke functions that do not take arguments):

in JSObjectHelper:
public static native Object invoke(JSObject object, String name) /*-{
  return object[name].apply(object);
 }-*/;


in JSObject:
public final Object invoke(String name) {
  return JSObjectHelper.invoke(this, name); };

invoking toString of Size:
public String toString(){
  return (String) getJSObject().invoke("toString");
}

As you might have notice an Object is returned.by the
JSObjectHelper/JSObject return methods. Returning a JSObject did not work,
because that cannot be cast to a String and I also could not get a working
narrowToString function on JSObject. It is a bit vague to my why returning
Object did work. As an implementation of narrowToString I tried:

public static native String narrowToString(JSObject object) /*-{
  return object; //Gives a ClassCast exception
 }-*/;

Although this works, and I can image it works with your way to pass
arguments, I can foresee some uglyness when an integer or float is returned
from the invoked function. Right now a lot of the API works with primitives
and there is a mismatch between Object and primitives. I'd rather avoid
autoboxing so then you may get things like:

Float f = (Float) getJSObject().invoke("getHeight");
return f.floatValue();

An uglier problem is how to combine this with the possibility that a complex
Javascript object is returned, because that would have to be returned as a
JSObject. In Java functions with the same signature but different return
tyehpes are not allowed, so we cannot have both:
public final Object invoke(String name){ ... };
public final JSObject invoke(String name){ ... };