IronPython CLR __clrtype__ manipultaion example

ipy_clr_test.py

# from http://devhawk.net/2009/04/21/__clrtype__-metaclasses-ironpython-classes-under-the-hood/

import clr
clr.AddReference('Microsoft.Scripting.dll')
clr.AddReference('Microsoft.Dynamic.dll')
clr.AddReference('IronPython.dll')

from Microsoft.Scripting.Generation import Snippets
from System.Reflection.Emit import OpCodes
from System.Reflection import FieldAttributes
from IronPython.Runtime.Types import ReflectedField

class ClrTypeMetaclass(type):
    def __clrtype__(cls):
        baseType = super(ClrTypeMetaclass, cls).__clrtype__()
        typename = cls._clrnamespace + "." + cls.__name__ if hasattr(cls, '_clrnamespace') else cls.__name__
        
        typegen = Snippets.Shared.DefineType(typename, baseType, True, False)
        typebld = typegen.TypeBuilder
        
        for ctor in baseType.GetConstructors():
            ctorparams = ctor.GetParameters()
            ctorbld = typebld.DefineConstructor(ctor.Attributes, ctor.CallingConvention, tuple([p.ParameterType for p in ctorparams]))
            ilgen = ctorbld.GetILGenerator()
            ilgen.Emit(OpCodes.Ldarg, 0)
            for index in range(len(ctorparams)):
                ilgen.Emit(OpCodes.Ldarg, index + 1)
            ilgen.Emit(OpCodes.Call, ctor)
            ilgen.Emit(OpCodes.Ret)
        
        if hasattr(cls, "_clrfields"):
            for fldname in cls._clrfields:
                typebld.DefineField(fldname, clr.GetClrType(cls._clrfields[fldname]), FieldAttributes.Public)
        
        new_type = typebld.CreateType()
        
        if hasattr(cls, "_clrfields"):
            for fldname in cls._clrfields:
                fldinfo = new_type.GetField(fldname)
                setattr(cls, fldname, ReflectedField(fldinfo))
        return new_type
        
class Product(object):
    __metaclass__ = ClrTypeMetaclass
    _clrnamespace = "DevHawk.IronPython.ClrTypeSeries"
    _clrfields = {
        'name': str,
        'cost': float,
        'quantity': int,
    }
    
    def __init__(self, name, cost, quantity):
        self.name = name
        self.cost = cost
        self.quantity = quantity
        
    def calc_total(self):
        return self.cost * self.quantity
        
p = Product('Crunchy Frog', 5.99, 10)
t = p.GetType()
print(p.name)
namefi = t.GetField('name')
print(namefi.GetValue(p))
namefi.SetValue(p, 'Spring Supprise')
print(p.name)