[IronPython] Constructors & inheriting from standard .NET classes

[Michael Foord]

Dino Viehland wrote:
> You need to override and call the base __new__ instead of __init__.  .NET has a simpler construction model than Python does and __new__ is what best corresponds to .NET constructors.
>
> class Derived(Test.Base):
>     def __new__(cls, i):
>         return Test.Base.__new__(cls, i)
>
> d = Derived()
>   

Won't that still blow up? What will .NET use for i in the constructor if 
you don't provide an argument?

Michael

>
> From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Zach Crowell
> Sent: Friday, August 21, 2009 4:39 PM
> To: users at lists.ironpython.com
> Subject: [IronPython] Constructors & inheriting from standard .NET classes
>
> I am unable to inherit from .NET classes which do not define a parameterless constructor.  Is this expected behavior? Is there another way to make this inheritance work?
>
> Here's a simple case.
>
> using System;
>
> namespace Test
> {
>     public class Base
>     {
>         public Base(int i)
>         {
>         }
>     }
> }
>
> import clr
> clr.AddReference('Test')
> import Test
>
> class Derived(Test.Base):
>     def __init__(self):
>         pass
>
> d = Derived()
>
> Traceback (most recent call last):
>   File "d:\tmp\class.py", line 9, in d:\tmp\class.py
> TypeError: Derived() takes exactly 2 arguments (1 given)
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>   


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