Accessing my extension methods from Python Component

Hi I have written some extension methods for the Rhino.Geometry.Transform struct but am not sure how to access it from the Python component within Grasshopper ( I remember getting it to work once but not sure why it broke down again).

I have a the following code written in C#:

namespace blahblah.Extensions{

public static class TransformMethods{

public static AxisAngle ToAxisAngleRepresentation (this Transform m){

//Implemented code here

}

I have several methods to extend Transform struct, in order to convert 4x4 matrices into different formats e.g. axis-angle representation. In this case the return AxisAngle is one of my custom structs. My desire is to script completely in Python from Grasshopper. However I cannot seem to access these extension methods from there.

I have done the following:

1) I compile "blahblah.dll" and place it in my Grasshopper components directory.

2) To test it I use a C# component and reference the dll from "manage assemblies". The C# component automatically adds "using blahblah.Extensions". I feed in a Transform struct called m and am able to call m.ToAxisAngleRepresentation() without errors. Everything is good. (except maybe intellisense doesn't pick it up the method)

3) Next I wish to do the same thing in a Python component. (Here I am still confused about referencing external libraries). I first add my bin/release folder (where blahblah.dll is located) to my sys.path.

4) Next I add clr.AddReference("blahblah.dll")

5) I add the following line:

from blahblah.Extensions import *

which I would assume is equivalent to "using blahblah.Extensions" in the C# component

6) I then test with the following code:

m = Transform()

m.ToAxisAngleRepresentation()

7) I get the following error: Runtime error (MissingMemberException): 'Transform' object has no attribute 'ToAxisAngleRepresentation'

A further question I have with Python components. If I copy my dlls into the Grasshopper component folders. Do I still need to perform steps 3 and 4?

Thanks!

Replies to This Discussion

Permalink Reply by Benjamin Golder on January 10, 2013 at 9:33am

It looks like you set up your paths correctly for importing your dll to IronPython, so the problem is either:

1. a difference in the actual object you are using in C# vs. Python - perhaps you aren't calling .ToAxisAngleRepresentation() on the same type of object.

2. Classes are read and compiled differently between C# and IronPython.

With regard to copying your dlls into the component folders: Last I checked, the component folders are not in sys.path by default (though I think they should be), so you would still have to do steps 3 and 4.

You may want to post your code in C# and IronPython separately, as a brief test calling .ToAxisAngleRepresentation() in both languages somewhere where others can see it. Paste it into a gist or post it on StackOverflow. Show the same code calling the same method in both.

Permalink Reply by Jason Lim on January 12, 2013 at 8:46pm

Hi Benjamin,

Thank you for taking the time to reply. I have found the solution, which I did before but somehow forgot. The key is to use clr.ImportExtensions which is provided by IronPython 2.7

So the above code should be:

import clr

clr.AddReference("blahblah.dll")

import blahblah.Extensions

clr.ImportExtensions(blahblah.Extensions) #Import my namespace

import Rhino.Geometry as rg

Transform t = rg.Transform()

t.ToAxisAngleRepresentation() #Yay it works

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