On Friday, September 21, 2012 1:16:56 PM UTC+2, js402882 wrote:
>
> Is there any way get info if JavaScriptObject is one of defined overlay
> objects?
> Example:
> I have native factory method which creates JavaScriptObjects:
>
> class WeirdFactory
> {
> native JavaScriptObject create(String type)
> {
> if (type == "car") return { name: "e46", maker: "bmw", seats: "4"}
> else if (type == "table") return { material: "wood", color:
> "brown"}
> else if (type == "type i forgot to crate overlay object for")
> return { id: "someId", name: "someName" }
>
> return null;
> }
> }
>
> class Car extends JavaScriptObject
> {
> native String name() /*-{ return this.name; }-*/;
> native String maker() /*-{ return this.maker; }-*/;
> native int seats() /*-{ return this.seats; }-*/;
> }
>
> class Table extends JavaScriptObject
> {
> native String material() /*-{ return this.material; }-*/;
> native String color() /*-{ return this.color; }-*/;
> }
>
> Now I want to use this factory to create overlay objects:
>
> <T> void getValue(Class<T> returnType, Callback<T> callback, String type)
> {
> JavaScriptObject value = weirdFactory.create(type);
>
> // Here I need something like
> // if (!JavaScriptObject.isDefined(value))
> // {
> // *handleUndefinedJSO(value);* // or throw new
> IllegalArgumentException("Undefined overlay object")
> // }
>
> T returnValue = (T)value;
> *
> *
> * *callback.returned(returnValue)
> }
>
> I need somehow check if *value* JavaScriptObject has defined custom
> overlay object (... extends JavaScriptObject)
> In pure Java I would catch ClassCastExcetion. But this does not work with
> JavaScriptObject which simply casts to anything (from it's nature, it's
> JavaScript object in the end after compilation).
>
> Does anybody have idea how to get info if JavaScriptObject is one of
> defined overlay objects?
>
>
There's nothing like "defined overlays for a given JS object". Overlays are
only a Java API to access a native JS object.
For instance, "Car car = weirdFactory.create("table")" is perfectly legal,
and car's getters will simply return null/undefined. And then you can do
"Table table = car.cast()".
You don't have a notion of "type" on your created objects, so you won't
have that in Java either. I mean, in JS, with the same factory, how would
you tell if you have a "table" or a "car"? if you had constructor functions
for the objects (new Table, new Car), you could do instanceof checks (in
JS). Or you could have a "type" property on your objects, so you could
getType() in Java to do conditional processing.
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