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Support overriding protected virtual methods of a .NET class in Python #2192
Description
Based on https://stackoverflow.com/questions/75514392 by IkeStarnes.
Environment
- Pythonnet version: 3.0.1
- Python version: 3.10 64-bit
- Operating System: Windows 11
- .NET Runtime: 6.0
Details
Given the following C# code for the .NET class:
namespace MyTestLib
{
public class MyTestClass
{
private int _x;
public MyTestClass(int inNumber) { SetNumber(inNumber); }
public int GetNumber()
{
Console.WriteLine(string.Format(".NET MyTestClass.GetNumber: {0}", _x));
return _x;
}
public void SetNumber(int inNumber)
{
_x = inNumber;
Console.WriteLine(string.Format(".NET MyTestClass.SetNumber: {0}", _x));
}
protected virtual void OnUseNumber(int inNumber) { }
public void UseNumber(int inNumber)
{
Console.WriteLine(string.Format(".NET MyTestClass.UseNumber: {0}", inNumber));
OnUseNumber(inNumber);
}
}
public class MyTestClass2 : MyTestClass
{
MyTestClass2() : base(55) { }
protected override void OnUseNumber(int inNumber)
{
SetNumber(inNumber * 4000);
Console.WriteLine(string.Format("MyTestClass2.OnUseNumber: {0}", GetNumber()));
}
}
}I've tried the following Python code, but the OnUseNumber is never called:
class MySubClass(MyTestLib.MyTestClass):
def __init__(self):
super().__init__(99)
def OnUseNumber(self, inNumber):
self.SetNumber(inNumber * 4000)
print ("Python MySubClass.OnUseNumber: {}".format(self.GetNumber()))
main():
myclass = MyTestLib.MyTestClass(10)
print("Before use: {}".format(myclass.GetNumber()))
myclass.UseNumber(5)
print("After use: {}".format(myclass.GetNumber()))
myclass2 = MyTestLib.MyTestClass2()
print("Before use: {}".format(myclass2.GetNumber()))
myclass2.UseNumber(5)
print("After use: {}".format(myclass2.GetNumber()))
mysubclass = MySubClass()
print("Before use: {}".format(mysubclass.GetNumber()))
mysubclass.UseNumber(5)
print("After use: {}".format(mysubclass.GetNumber()))
Activity
mhsmith commentedon Jul 11, 2023
If
OnUseNumberwaspublic virtual, then this could probably be fixed by adding a__namespace__attribute to the Python class, as in #567 (comment).However, based on this discussion, overriding
protected virtualmethods is not currently supported. I think this is because of the use of the zero-argument form ofGetMethodshere, which only returns public methods.This particularly affects Winforms, which has a lot of
protected virtualmethods.WndProc()method onFormcontrol in WinForms is never getting called #2536 as a duplicate of this issue