From: mattmsykes@... (Matt M Sykes)
Date: 2002-04-24T18:56:43+09:00
Subject: Re: building extensions-- new vs initialize

Dennis Newbold <dennisn@pe.net> wrote in message news:<Pine.GSO.3.96.1020423113412.4613A-100000@shell2>...
> Hi Norman,
> 
>      Try using SWIG to build your extension.  Some on this list have
> had a few problems getting the resulting code to run properly, (then
> again, it may).  But you can look at the generated code startup logic
> (entry point Init_<extension-name), I believe) as a good example of
> how to define the necessary entry points, constants, class linkages,
> etc.).  You can get SWIG for free from www.swig.org
> 
> Dennis
> 
> On Tue, 23 Apr 2002, Norman Makoto Su wrote:
> 
> > Hi, I'm trying to build a ruby extension in C.  While looking at the pickaxe CD
> > player example, I noticed that they define a singleton_method called "new" and
> > then a normal method called "initialize".  What is the motivation for this?  Is
> > it so that when you call CDPlayer.new, the returned object is of type Data?
> > (this can't be achieved with just initialize?)
> > 
> > I'm confused as to when it is or not neccessary to define a "new" method in
> > addition to an "initialize" method.  For example, when defining class variables,
> > does this have to be done in a "new" method, since the class has not been
> > instantiated?
> > 
> > One last thing, would someone mind giving me the an example of the correct way
> > to make a class that includes the Singleton method and then define the
> > "instance" method (using rb_require, rb_include_module, etc...)
> > 
> > Thank you, please excuse my inexperience,
> > 
> > --
> > Norman
> >

I tried SWIG last week.  I think the Ruby C API is elegant and
easy enough to not need SWIG.

For a sample C++ class with three methods, SWIG produced 700 lines 
of code for the binding to Ruby --- and it didn't even work.

A hand-written wrapper was 20 lines and worked flawlessly.  By
writing the bindings yourself you can also design a more intelligent
interface to Ruby; for example you may want a "method!" or a 
"method?" or a "method(&block)".

I can see using SWIG to create bindings for Python, since you 
can't make classes inside the Python C API (among other things).

So to me, SWIG is sort of a kluge for languages that have a less
enlightened C API :)

--Matt