From: Richard Dale <Richard_Dale@...>
Date: 2004-08-17T19:11:01+09:00
Subject: Re: Embedding Ruby as plugin

Tobias Grimm wrote:

> Hi!
> 
> I have an application written in C++, that provides a plugin interface.
> What I would like to do now, is to implement a plugin, that allows to
> execute a ruby script, like this:
> 
> 1) Application loads plugin.so
> 2) Application invokes plugin
> 3) Plugin creates object "interface" of class Interface
> 4) Plugin loads rubyscript.rb
> 5) rubyscript.rb uses interface object created in 3) to send messages to
> the plugin
> 
> I used SWIG to create a wrapper for the Interface class that the ruby
> script should use. If I simply wanted to create an ruby extension, the
> wrapper should just be compiled to a lib, that ruby can load with a
> require statement. But now the wrapper is part of the plugin, which itself
> is loaded by the application. How do I get the ruby script know about the
> Interface class and the interface object to use?
I'm not familiar with the code generated by SWIG, but you can start ruby and
define a class from C like this:

    ruby_init();
    ruby_run();

    interface_module = rb_define_module("Interface");
    interface_class = rb_define_class_under(interface_module, "Interface",
                                            rb_cObject);

    # I assume Swig generates various wrapper methods like this:
    rb_define_method(interface_class, "foobar", foo_bar, 1);
 ...


    rb_require("rubyscript.rb");
    
    # Call an initialization method to create the "interface" instance
    rb_funcall(interface_class, rb_intern("init_rubyscript"), 0);

-- Richard