Hey yall
Seems IronRuby objects do not yet work with WPF databinding. One
approach to
a workaround is to emit a wrapper type that defines CLR properties. When
WPF
calls the getter/setter the call is forwarded ot the contained contained
ruby object. This will allow defining business objects in ruby and
databing
them to the UI.
This might be useful to thers, so here is my approach. The first part is
C#
code that defines a type given a list of property names. The second part
is
ruby code that creates a wrapper instance for a given ruby object and
caches
the type so that you dont generate a type for each element in an array…
The C# code to generate a type:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Reflection.Emit;
namespace GenerateType
{
public class TypeGenerator
{
public delegate object GetPropertyDelegate(string propertyName);
public delegate object SetPropertyDelegate(string propertyName,
object value);
public static Type Generate(string className, List<string>
properties)
{
AssemblyName asmName = new AssemblyName(“BindingTypes”);
AssemblyBuilder asmBuilder =
AppDomain.CurrentDomain.DefineDynamicAssembly(asmName,
AssemblyBuilderAccess.Run);
ModuleBuilder modBuilder =
asmBuilder.DefineDynamicModule(“Types”);
TypeBuilder typeBuilder = modBuilder.DefineType(className,
TypeAttributes.Public |
TypeAttributes.Class |
TypeAttributes.AutoClass |
TypeAttributes.AnsiClass |
TypeAttributes.BeforeFieldInit |
TypeAttributes.AutoLayout);
FieldBuilder getFieldBuilder =
typeBuilder.DefineField(“OnGet”,
typeof(GetPropertyDelegate), FieldAttributes.Public);
FieldBuilder setFieldBuilder =
typeBuilder.DefineField(“OnSet”,
typeof(SetPropertyDelegate), FieldAttributes.Public);
MethodAttributes getSetAttr =
MethodAttributes.Public |
MethodAttributes.SpecialName |
MethodAttributes.HideBySig;
foreach (string propertyName in properties)
{
PropertyBuilder propBuilder =
typeBuilder.DefineProperty(propertyName, PropertyAttributes.None,
typeof(object), new Type[] {});
MethodBuilder getter =
typeBuilder.DefineMethod("get_" +
propertyName,
getSetAttr,
typeof(string),
Type.EmptyTypes);
ILGenerator ilGen = getter.GetILGenerator();
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldfld, getFieldBuilder);
ilGen.Emit(OpCodes.Ldstr, propertyName);
ilGen.Emit(OpCodes.Callvirt,
typeof(GetPropertyDelegate).GetMethod(“Invoke”));
ilGen.Emit(OpCodes.Ret);
// Define the "set" accessor method for CustomerName.
MethodBuilder setter =
typeBuilder.DefineMethod("set_" + propertyName,
getSetAttr,
null,
new Type[] {
typeof(string)
});
ilGen = setter.GetILGenerator();
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldfld, setFieldBuilder);
ilGen.Emit(OpCodes.Ldstr, propertyName);
ilGen.Emit(OpCodes.Ldarg_1);
ilGen.Emit(OpCodes.Callvirt,
typeof(SetPropertyDelegate).GetMethod(“Invoke”));
ilGen.Emit(OpCodes.Pop);
ilGen.Emit(OpCodes.Ret);
// Last, we must map the two methods created above to
our
PropertyBuilder to
// their corresponding behaviors, “get” and “set”
respectively.
propBuilder.SetGetMethod(getter);
propBuilder.SetSetMethod(setter);
}
return typeBuilder.CreateType();
}
}
}
And here is the ruby code to generate the wrapper type
require ‘mscorlib’
require ‘C:\Documents and Settings\Josh\My Documents\Visual Studio
2008\Projects\GenerateType\GenerateType\bin\Release\GenerateType.dll’
require ‘PresentationFramework, Version=3.0.0.0,Culture=neutral,
PublicKeyToken=31bf3856ad364e35’
require ‘PresentationCore, Version=3.0.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35’
require ‘WindowsBase, Version=3.0.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35’
include System
include System::Collections::Generic
include GenerateType
include System::Collections::ObjectModel
include System::Windows
include System::Windows::Controls
include System::Windows::Data
include System::Windows::Input
class WrapperGenerator
def initialize
@wrapper_cache = {}
end
def wrap(ruby_object)
if ruby_object.is_a? Array
ruby_object.map {|o| wrap(o) }
else
cache(ruby_object) unless cached(ruby_object)
wrapper_class = cached(ruby_object)
wrapper_class.new(ruby_object)
end
end
def invalidate
@wrapper_cache.clear
end
private
def cached(object)
@wrapper_cache[object.class.name]
end
def cache(object)
@wrapper_cache[object.class.name] = generate_wrapper(object)
end
def generate_wrapper(object)
wrapper_name = “#{object.class.name}Wrapper”
properties = List.of(System::String).new
(object.methods - Object.instance_methods).each {|m| properties.add
m.to_s}
wrapper_base_type = TypeGenerator.generate("#{wrapper_name}Base",
properties)
base_instance = Activator.create_instance wrapper_base_type
eval <<EOS
class #{wrapper_name} < base_instance.class
def initialize(original)
self.on_get = lambda do |prop|
original.send prop
end
self.on_set = lambda do |prop, val|
original.send "\#{prop}=", val
end
end
end
return #{wrapper_name} # return the class
EOS
end
end
class Person
attr_accessor :first_name, :last_name
def initialize(first_name, last_name)
@first_name, @last_name = first_name, last_name
end
def full_name
“#{last_name}, #{first_name}”
end
end
A sample UI
people = []
10.times { |n| people << Person.new(“John #{n}”, “Smith”) }
wrapper = WrapperGenerator.new
w = Window.new
combo = ComboBox.new
combo.items_source = wrapper.wrap(people) # wrap people objects
combo.display_member_path = “full_name”
combo.margin = 20
w.content = combo
Application.new.run w
