From: Rick Bradley <rick@...>
Date: 2002-05-07T02:55:41+09:00
Subject: Re: Embedding Ruby in C++

* jared l. jennings (jjenning@stetson.edu) [020506 12:46]:
> this is how i thought of it: you wrap the classes you want to get at in
> ruby. now, instead of using 'require' to bring them in from a .so, you
> compile the wrappers into the C++ program. When the program runs, it
> initializes the ruby interpreter which it embeds, then calls the Init
> function for the wrapper, thus making the wrapped classes available to
> the embedded Ruby.  Then in C++ when you want to get at objects created
> or modified by Ruby, you get a VALUE for them, and... ahm... i think you'd
> have to look at the wrapper code, but i think SWIG makes a struct that
> has a pointer to the C++ object. somewhere in there there is a pointer
> you can snag. so you can mess with the object, and the changes are
> visible to the embedded Ruby. you can frob it in ruby, and see changes
> in C++. both in an object-oriented way without an overage of C-writing.

I used to do a lot of embedding of Perl into C/C++ and C/C++ into Perl,
using SWIG for the latter (actually once I had a C program embed a Perl
interpreter which called SWIG'ed C extensions, but it was not something
I wanted to do a lot of).

At least there (I don't know how it's done w/ Ruby) if you wanted to
embed the Perl interpreter into a C/C++ application you included an .h
file in your C/C++ source, used some macros to initialize the
interpreter, and used some more macros to call Perl routines and pass
values back and forth.  You linked with -lperl (IIRC) and ended up with
a big gnarly binary.  This is the direction I think the original poster
was wanting to go -- and I'm curious how to do the same thing with Ruby
myself.

Going the other way (what I'm reading you as saying) one writes some
C/C++ code and then would like to call that functionality from Ruby,
uses SWIG to generate the proper stubs, compiles the stubs+C/C++ and
then does a require from Ruby.

Rick
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