How to pass a lambda expression to a C# constructo

问题:

I'm integrating an IronPython scritping engine into my C# raytracer which, so far, has been a breeze even though I'm completely new to Python. There is one particular thing, though, that I need help with. I have a C# class which defines a constructor like this:

public CameraAnimation(Action<Camera, float> animation)

In C#, I would instantiate this like so:

var camAnimation = new CameraAnimation((camera, time) => camera.Position += new Vector(1, 0, 0));

I can't quite figure out how to make a similar assignment for the Action object in IronPython, so how would the Python syntax look?

回答1:

Assuming I interpreted this right, and Action is a generic delegate, the below works (the stubs I used are included).

Python:

import clr
clr.AddReference("IronPythonDelegates")

import IronPythonDelegates

def camActionPy(camera, time):
  print "Camera: " + str(camera) + ", time: " + str(time)

IronPythonDelegates.CameraAnimation(camActionPy);

CSharp:

namespace IronPythonDelegates
{
    public class Camera{}

    public class CameraAnimation
    {
    private System.Action<Camera, float> animation;

    public CameraAnimation(System.Action<Camera, float> animation)
    {
        this.animation = animation;
        this.animation(new Camera(), 1.5f);
    }
    }
 }

I corrected the above to use System.Action, and it no longer requires explicit reflection. It's a bit weird though. For some reason, I could construct a user-created delegate like:

explicitTestAction = IronPythonDelegates.TestAction[IronPythonDelegates.Camera, System.Single](camActionPy);
IronPythonDelegates.CameraAnimation(explicitTestAction);

but could not do so with System.Action. E.g. with

explicitSystemAction = System.Action[IronPythonDelegates.Camera, System.Single](camActionPy)
IronPythonDelegates.CameraAnimation(explicitSystemAction);

explicitSystemAction is null. TestAction was just defined as:

public delegate void TestAction<T1, T2>(T1 one, T2 two);

But luckily either way it's fine to just do:

CameraAnimation(System.Action) 

or

CameraAnimation(TestAction)

though for some reason I don't remember that working when I first tried...