# Extending modules defined in a ruby library via C# **URL:** \ **Category:** IronRuby\ **Created:** [January 31, 2009, 7:42pm UTC](https://www.ruby-forum.com/t/extending-modules-defined-in-a-ruby-library-via-c/159114 "2009-01-31T19:42:16Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\ **Post date:** [January 31, 2009, 7:42pm UTC](https://www.ruby-forum.com/t/extending-modules-defined-in-a-ruby-library-via-c/159114/1 "2009-01-31T19:42:16Z")
Hi, I think I’ve stumbled on a bug of IronRuby, but I would like to hear your thoughts about this before filing a report on the bug tracker as I might be missing something or doing something wrong. I have a ruby library in which is defined a module and this module holds a few classes and constants. Then I wrote a library in C# where the same module is defined to add more classes other than the ones defined on the ruby side. Now if I load the assembly first and then i require my ruby library everything works fine, but if I require the ruby library first and then load the assembly, the module defined by the ruby lib gets totally wiped off leaving there only what was defined in the assembly. Given that in similar scenarios we obviously can’t use Extends = typeof(…) in the RubyModuleAttribute, shouldn’t modules previously defined in ruby code be automatically extended instead of being erased/redefined (which is definitely broken)? Right below here you can find the code to reproduce and verify the reported behaviour (for convenience I also made an attachment to this mail). # =========== foo.rb =========== def test(a) a.each{ |s| puts “#{s} is #{begin eval(s); rescue NameError; ‘undefined’ end}”} end module Foo class Bar; end VERSION = 1 end /\* ======== Nrk.Foo.Test.cs ======== \*/ namespace Nrk.Foo.Test { [RubyModule] public static class Foo { [RubyClass] public static class Hoge { [RubyMethod(“piyo?”, RubyMethodAttributes.PublicSingleton)] public static bool Piyo(Object self) { return true; } } } } # =========== test\_assembly\_first.rb =========== load\_assembly ‘Nrk.Foo.Test’, ‘Nrk.Foo.Test’ require ‘foo.rb’ test [‘Foo’, ‘Foo::Bar’, ‘Foo::VERSION’, ‘Foo::Hoge’, ‘Foo::Hoge.piyo?’] # =========== test\_ruby\_first.rb =========== require ‘foo.rb’ load\_assembly ‘Nrk.Foo.Test’, ‘Nrk.Foo.Test’ test [‘Foo’, ‘Foo::Bar’, ‘Foo::VERSION’, ‘Foo::Hoge’, ‘Foo::Hoge.piyo?’] # =========== OUTPUT #1 =========== Foo is Foo Foo::Bar is Foo::Bar Foo::VERSION is 1 Foo::Hoge is Foo::Hoge Foo::Hoge.piyo? is true # =========== OUTPUT #2 =========== Foo is Foo Foo::Bar is undefined Foo::VERSION is undefined Foo::Hoge is Foo::Hoge Foo::Hoge.piyo? is true ---
**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\ **Post date:** [February 1, 2009, 1:13am UTC](https://www.ruby-forum.com/t/extending-modules-defined-in-a-ruby-library-via-c/159114/2 "2009-02-01T01:13:03Z")
.NET types can never be 100% compatible with Ruby classes; the semantics are simply too different. What would you expect to happen, for instance, if you were to say the following: module System::IDisposable; end class System::Collections::ArrayList; include System::IDisposable; end; x = System::Collections::ArrayList.new require ‘mscorlib’ Clearly, the “real” System::Collections::ArrayList can’t implement IDisposable because the type is immutable. And the type we created to represent the variable x can’t be a “real” ArrayList because we didn’t know about that class when x was allocated. So this leaves us with two possibilities: 1. Always overwrite the previously defined constants with the newly imported CLR types 2. Fail to load the redefined types …and we’re currently doing the first. While it seems reasonable to fail, it raises questions about what to do if 40 types can be loaded successfully but one can’t be. Do we raise an exception even though there were 40 successes? Or do we fail to load any types at all? Monkey-patching CLR types is never going to be able to work identically to monkey-patching pure Ruby types. ---
**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\ **Post date:** [February 1, 2009, 7:58am UTC](https://www.ruby-forum.com/t/extending-modules-defined-in-a-ruby-library-via-c/159114/3 "2009-02-01T07:58:55Z")
That’s absolutely true for arbitrary CLR types. Library types (those marked by RubyClass attribute) are handled differently though. They can be seen like collections of extension methods. So it makes sense to extend a Ruby class using library methods. So far we were focused on extending CLR types using library types. Extending Ruby classes could be seen as a feature that is not implemented yet. Could you file a feature request (bug) on RubyForge? A possible workaround for you: define a C# method that takes a Ruby class and extends it in manually using methods on RubyModule/RubyClass (AddMethod etc.). You would call this helper after loading the assembly. Tomas ---
**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\ **Post date:** [February 1, 2009, 10:59am UTC](https://www.ruby-forum.com/t/extending-modules-defined-in-a-ruby-library-via-c/159114/4 "2009-02-01T10:59:08Z")
On Sun, Feb 1, 2009 at 07:30, Tomas M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > That’s absolutely true for arbitrary CLR types. Library types > (those marked by RubyClass attribute) are handled differently > though. They can be seen like collections of extension methods. > So it makes sense to extend a Ruby class using library methods. In fact, I think the described behaviour is perfectly fine for CLR types and I was sort of expecting this, but not for those types marked by RubyClass. > So far we were focused on extending CLR types using library > types. Extending Ruby classes could be seen as a feature that > is not implemented yet. Could you file a feature request (bug) on > RubyForge? OK, I will file it later. Maybe I will assign a lower priority to this as I guess it is not really a common scenario and I don’t know how many folks are trying to build extension libs for IronRuby. But still, IMHO it would be nice to get this fixed before going 1.0. > A possible workaround for you: define a C# method that takes > a Ruby class and extends it in manually using methods on > RubyModule/RubyClass (AddMethod etc.). You would call this > helper after loading the assembly. Yeah I was thinking about something along that way, I was just waiting for confirmations before going on. FYI I got into this particular case while porting Florian F.'s json library (see [http://json.rubyforge.org/](http://json.rubyforge.org/)) which provides two variants for the core bits, namely “extension” (implemented in C) or “pure” (ruby). Both relies on a few methods, classes and constants previously defined in the same module in which they are loaded (JSON). When loading the JSON::Ext::Parser, I was getting everything in JSON and JSON::Ext erased. require ‘json/common’ module JSON module Ext # require ‘json/ext/parser’ # require ‘json/ext/generator’ ``` load_assembly 'IronRuby.Libraries.Json', 'IronRuby.Libraries.Json' $DEBUG and warn "Using c extension for JSON." JSON.parser = Parser JSON.generator = Generator ``` end end I could also define the Parser and Generator classes into a different global module and then assign them (e.g. JSON.parser = IronJson::Ext::Parser), but well there is no fun doing this 🙂 – Daniele A. [http://www.clorophilla.net/blog/](http://www.clorophilla.net/blog/)