On Sep 13, 8:22 pm, wolffiex <[EMAIL PROTECTED]> wrote:
> Hi everyone,
> I found a little surprising behavior today with Rhino. I don't know if
> this is a bug; I'm hoping someone will weigh in. It appears that
> instanceof doesn't work on objects from a foreign scope. I assume this
> is because instanceof just looks up the prototype chain, but I wonder
> if that is the correct implementation, given the fact that you can
> pass objects from one scope to another using Rhino and Java. Here's my
> little testcase:
>
> import org.junit.Test;
> import org.mozilla.javascript.ContextFactory;
> import org.mozilla.javascript.Context;
> import org.mozilla.javascript.Scriptable;
> import org.mozilla.javascript.ScriptableObject;
>
> public class ObjectSurprise {
> @Test
> public void showBug(){
> ContextFactory factory = new ContextFactory();
> Context cx1 = factory.enterContext();
> Context cx2 = factory.enterContext();
> final Scriptable scope1 = cx1.initStandardObjects();
>
> cx1.evaluateString(scope1,
> "tryMe = function(){return {};}",
> "tryMe", 1, null);
>
> Scriptable result = (Scriptable)
> ScriptableObject.callMethod(scope1, "tryMe", new Object[]
> {});
>
> String throwIfNotObject =
> "isObject = function(obj){ if( !(obj instanceof
> Object)) throw('not an object');}";
>
> cx1.evaluateString(scope1, throwIfNotObject, "isObject", 1,
> null);
> Object [] arg = { result };
>
> //doesn't throw, as expected
> ScriptableObject.callMethod(scope1, "isObject", arg);
> Context.exit();
>
> final Scriptable scope2 = cx2.initStandardObjects();
> cx2.evaluateString(scope2, throwIfNotObject, "isObject", 1,
> null);
>
> //throws -- unexpected
> ScriptableObject.callMethod(scope2, "isObject", arg);
> Context.exit();
> }
>
> }
You're right: instanceof just walks up the prototype chain looking for
the object. Mixing objects from two separate initStandardObject calls
is problematic in general; why do you need to do this?
--N
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