[IronPython] IronLanguages

Matthias nitro at dr-code.org
Tue Mar 29 20:57:38 CEST 2011

Am 29.03.2011, 19:27 Uhr, schrieb Dino Viehland <dinov at microsoft.com>:

> Just to chime in on how to do the conversion: the answer is that you  
> probably can't, at least not for something like TestClass.  You could  
> look at what sort of type you're converting from in JS (number, string,  
> function, etc...) and see if TestClass has any implicit conversions to  
> it from primitive .NET types (double, string, delegate, etc...) and if  
> so you could invoke one of those conversions.  But most likely you won't

This is what I am doing now already and it works quite nicely for simple  

> be able to convert directly to TestClass.  If TestClass was something  
> more like IList then you could do a conversion there as well.  The only  
> way you're likely able to convert to TestClass is if the user got a  
> TestClass object from .NET, brought it into JS (where you wrapped it in  
> some object of your own), and then you brought it back to .NET - but  
> then when you bring it back to .NET you should bring it back as the real  
> TestClass instead of your wrapped TestClass.

Yes, I have thought to force users to "inherit" from (use a prototype  
object) which comes from .net.

> The only other way would be figuring out somehow to allow a JavaScript  
> developer to subclass a .NET TestClass type.  We allow this in  
> IronPython via our NewTypeMaker class but we are lucky in that  
> everything is in the .NET world.  One way you could go about this is  
> having a function like CreateClass which takes a subtype (TestClass) and  
> a dictionary of string -> JS functions which you then call into for the  
> implementation of the various subclass methods.  You would then have a  
> .NET type which is being extended by JavaScript - there's probably going  
> to be some fun and tricky problems in doing this though.  Then the user  
> can call the resulting class you give them, they'll get an instance  
> which is wrapped in JavaScript, and when you pass it back to .NET you  
> can unwrap it.

Yes, this was my main idea. It's very similar how SWIG directors handle  
cross-language polymorphism. At runtime I'd create a class which derives  
 from TestClass and which overrides all virtual methods and properties. The  
C# overrides would call the JSObject to see if there's a javascript  
implementation for them. If there is, it will call the javascript  
implementation, otherwise it will call the base class's (TestClass in the  
example) implementation.


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