# C++ pointers to Ruby objects **URL:** \ **Category:** Ruby\ **Created:** [December 17, 2009, 4:42pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334 "2009-12-17T16:42:40Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 17, 2009, 4:42pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/1 "2009-12-17T16:42:40Z")
I’m trying to make an interface between PhysX and Ruby and I got stucked on the very beggining. XD I have an NxPhysicsSDK pointer, pointing to an object (duh) and I would like to store this pointer into an Ruby VALUE object. I don’t really need to see it’s value outside the extension class (being clear: everything would be encapsulated), but I only find conversions from C pointers, not C++ objects. Does anyone have a tip? ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 17, 2009, 5:42pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/2 "2009-12-17T17:42:14Z")
You need to either build your own C wrapper around the C++ and expose that in Ruby as you cannot just map C++ objects to Ruby’s C-API. Or you use a tool like Rice ( [http://rice.rubyforge.org](http://rice.rubyforge.org) ) or SWIG to wrap the C++ into Ruby. I would also recommend looking into Rb++ ( [http://rbplusplus.rubyforge.org](http://rbplusplus.rubyforge.org) ) which IMO (though slightly biased) is easier to deal with than SWIG. Jason On Thu, Dec 17, 2009 at 10:42 AM, Yuri Albuquerque ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 17, 2009, 6:09pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/3 "2009-12-17T18:09:23Z")
Well, I installed Rice’s gem and when I try to run my extconf.rb it returns: extconf.rb:1:in `require’: no such file to load – mkmf-rice (LoadError) from extconf.rb:1 For some reason, Ruby is not finding this file. I’ll try with Rb++ and see what I get. ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 17, 2009, 6:19pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/4 "2009-12-17T18:19:11Z")
Yuri Albuquerque wrote: > Well, I installed Rice’s gem and when I try to run my extconf.rb it > returns: > > extconf.rb:1:in `require’: no such file to load – mkmf-rice (LoadError) > from extconf.rb:1 > > For some reason, Ruby is not finding this file. > > I’ll try with Rb++ and see what I get. Forget it. I forgot to include require ‘rubygems’ on my extconf.rb Thank you. But I’ll still try Rb++, too. ^^ ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 17, 2009, 8:41pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/5 "2009-12-17T20:41:16Z")
Well, I have two new doubts: 1 - When an object is created on PhysX, it’s not directly with a constructor. For example, if I want to create an NxPhysicsSDK object, I have to do this: NxPhysicsSDK \*sdk = NxCreatePhysicsSDK(NX\_PHYSICS\_SDK\_VERSION, 0, 0); What do I have to do to convert this on an initialize method on Rice? 2 - If I try to use Rb++, it asks for a namespace. PhysX does not use namespaces. What should I do in this case? Ignore this step? ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 18, 2009, 10:45pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/6 "2009-12-18T22:45:15Z")
Yuri Albuquerque wrote: > I’m trying to make an interface between PhysX and Ruby and I got stucked > on the very beggining. XD > > I have an NxPhysicsSDK pointer, pointing to an object (duh) and I would > like to store this pointer into an Ruby VALUE object. I don’t really > need to see it’s value outside the extension class (being clear: > everything would be encapsulated), but I only find conversions from C > pointers, not C++ objects. theoretically you should be able to store a struct in a ruby object that can contain pointers to anything. > **[GitHub - rdp/google\_hash: wrapper for google's hash functions, for ruby](https://github.com/rdp/google_hash)** > > wrapper for google's hash functions, for ruby. Contribute to rdp/google\_hash development by creating an account on GitHub. is an example project that has pointers to a C++ object [a google hash map]. The trick is wrapping all your ruby code in an extern “C” { } block. GL. -r ---
**Author:** ![denommus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e99b99/32.png) [@denommus](https://www.ruby-forum.com/u/denommus)\ **Post date:** [December 20, 2009, 10:04pm UTC](https://www.ruby-forum.com/t/c-pointers-to-ruby-objects/180334/7 "2009-12-20T22:04:21Z")
Roger P. wrote: > theoretically you should be able to store a struct in a ruby object that > can contain pointers to anything. > > [GitHub - rdp/google\_hash: wrapper for google's hash functions, for ruby](http://github.com/rdp/google_hash) > > is an example project that has pointers to a C++ object [a google hash > map]. > > The trick is wrapping all your ruby code in an extern “C” { } block. > > GL. > -r Thanks to your tip, I am very closer to what I want to do than ever. I didn’t needed to make any gluecode between C and C++, I’m writing directly gluecode between Ruby and C++. Thank you very much.