jython-users

[Jython-users] casting a java object created in jython to its true class

[Sells, F. <fr...@ad...>]

I use exec() in java to run some Python that defines gui elements.

I would like to get specific elements by name.

I can get do PyObject po = Python.get("xyz")

but I cannot cast this to anything but java.lang.Object

what am I missing here????

tia

fred

Re: [Jython-users] casting a java object created in jython to its true class

[brian z. <bz...@zi...>]

If you have a PyObject and want to get the underlying Java instance, use:

  po.__tojava__(<the Java class you want>)

For instance, say arg is a PyInteger instance, the following would get the
long value:

  long ticks = ((Number) arg.__tojava__(Number.class)).longValue();

Most subclasses (maybe all) of PyObject implement this method and try their
best to give you what you want.  It's amazing thorough for most types.

brian

----- Original Message -----
From: "Sells, Fred" <fr...@ad...>
To: "Jython (E-mail)" <jyt...@li...>
Sent: Monday, October 29, 2001 3:15 PM
Subject: [Jython-users] casting a java object created in jython to its true
class


> I use exec() in java to run some Python that defines gui elements.
>
> I would like to get specific elements by name.
>
> I can get do PyObject po = Python.get("xyz")
>
> but I cannot cast this to anything but java.lang.Object
>
> what am I missing here????
>
> tia
>
> fred
>
>
> _______________________________________________
> Jython-users mailing list
> Jyt...@li...
> https://lists.sourceforge.net/lists/listinfo/jython-users

Re: [Jython-users] casting a java object created in jython to its true class

[<bc...@wo...>]

[brian zimmer]

>If you have a PyObject and want to get the underlying Java instance, use:
>
>  po.__tojava__(<the Java class you want>)
>
>For instance, say arg is a PyInteger instance, the following would get the
>long value:
>
>  long ticks = ((Number) arg.__tojava__(Number.class)).longValue();

Just the smallest little nit about style: If arg isn't a number, the
line above will throw an ugly classcast exception. Normally it is better
to do:

   Object tmp = arg.__tojava__(Number.class):
   if (tmp != Py.NoConversion) {
       long ticks = ((Number) tmp).longValue();
   }

>Most subclasses (maybe all) ...

All subclasses that we want to use as arguments to java methods must
implement __tojava__().

regards,
finn