[Caml-list] Re: Native OCaml iPhone app now in iTunes Store

[Jeffrey Scofield <jeffsco@psellos.com>]

Joel Reymont <joelr1@gmail.com> writes:

> > All the code is in OCaml; there's no ObjC except in the (thin)
> > wrappers around the native iOS libraries.  We wanted to write as
> > much in OCaml as possible.
> 
> How did you wrap the native libraries then?

We went through a few iterations of plans for generating wrappers
automatically.  But we determined that automatically generated
wrappers that follow Objective C idioms are too cumbersome to use from
OCaml.  An automatic tool is going to require a lot of human input on
data structure choices, at the very least.

What we did in the end was to design a basic framework with an OCaml
class for each ObjC class.  The method APIs use idiomatic OCaml types
for values and collections.  The support code uses Cocoa foundation
classes to do dynamic method invocation, so the amount of ObjC code in
each wrapper is kept to a minimum (typically there is none).  The
framework lets us build individual wrappers quickly and keeps things
coherent and consistent.  We code up wrappers by hand as we need them.

> I've been meaning to write a Cocoa bridge for OCaml but haven't
> gotten to it yet.

It would be a big project.

> Are your wrappers available?

We'll be happy to release source to our Cocoa wrapper layer once we
recoup some of our investment in it.  In the meantime we can offer
advice on things that worked and didn't work for us.


Regards,

Jeffrey