[IronPython] Overriding derived methods

[Jonathan Jacobs]

Dino Viehland wrote:
> There's a bug in beta 5 and beta 6 where we can sometimes fail to call the correct derived method.  You can work around the bug in many cases w/:
> 
> Class MyForm(Form):
>         def __init__(self):
>                 self.OnKeyUp = self.OnKeyUp
>         def OnKeyUp(self, e):
>                 ...
> 
> Unfortunately you can still get some erattic behavior w/ the workaround in place.
> 
> This will be fixed for our beta 7 release.  This happens only when deriving from a type that has a large number of virtual methods, and unfortunately System.Windows.Forms hits this pretty heavily.

Thanks for the quick response, Dino. I've run into another (rather 
bizarre) situation, you'll need a few preliminary steps first:

1.) Create a vanilla "Windows Application" project in Visual Studio (C# 
2005 Express Edition, not sure if this matters)
2.) Compile it, add the compiled assembly to somewhere in your path.

I used the following code to reproduce the error:

 >>> clr.AddReferenceToFile('WindowsApplication1.exe')
 >>> from WindowsApplication1 import Form1
 >>> class MyForm(Form1):
...   def __init__(self):
...     self.OnKeyUp = self.OnKeyUp
...   def OnKeyUp(self, e):
...     print e
...
 >>> frm = MyForm()
 >>> Application.Run(frm)

Which yields the following output:

System.Windows.Forms.PaintEventArgs
System.Windows.Forms.KeyEventArgs
etc.

I'm really wondering about the PaintEventArgs object that sneaks in 
there. I haven't tried reproducing *all* of the generated C# code in 
pure IronPython code yet but the minimal form I mentioned in my previous 
email is not subject to this odd behaviour.

Regards
-- 
Jonathan