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Date: Thu, 3 May 2012 14:56:50 +0100
Message-ID: <CAOQwdX25S6Wjmf=g8f19cyvx6rUYxGEmGwFnUCNn612CvxmJFA@mail.gmail.com>
From: Joel Reymont <joelr1@gmail.com>
To: Goswin von Brederlow <goswin-v-b@web.de>
Cc: caml-list@inria.fr
Content-Type: text/plain; charset=ISO-8859-1
Subject: Re: [Caml-list] using modules to wrap c++ classes

Say I have a library class AdmCallbacks

class AdmCallbacks
     {
     public :
     AdmCallbacks();
     virtual ~AdmCallbacks();

     /*   ----------------------------------------------------------------   */

     virtual int Alert(AlertInfo * pInfo,
                       void *      pContext,
                       int *       aiCode) = 0;

     private :
     };

I subclass it and implement the Alert method to receive notifications.

I then create an instance of my derived class and pass it to some
initialization function so that the API knows to call the methods of
my instance.

My derived class may look like this

class MyAdmCallbacks: public AdmCallbacks
     {
     public :
     MyAdmCallbacks()  {};
     ~MyAdmCallbacks() {};

     /*   ----------------------------------------------------------------   */

     virtual int Alert(AlertInfo * pInfo,
                       void *      pContext,
                       int *       aiCode);
     };

int MyAdmCallbacks::Alert(AlertInfo * pInfo,
                          void *      pContext,
                          int *       aiCode)
     {
     int iIgnored;

     /*   ----------------------------------------------------------------   */

     cout << endl << endl;
     if (!pInfo -> dump(&iIgnored))
          {
          cout << "error in pInfo -> dump : " << iIgnored << endl;
          }

     /*   ----------------------------------------------------------------   */

     *aiCode = API_OK;
     return (OK);
     }

Now, suppose I want to implement the derived class on the OCaml side.

What is the best way to do it?

I can derive on the C++ side, keep a pointer to the OCaml instance
(self) in a member variable, instantiate MyAdmCallbacks in the
"MyAdmCallbacks_new" stub function which takes the OCaml self and then
set the member variable.

The Alert method on the C++ side would then dispatch to OCaml using
the stored OCaml self to call the Alert method as per 18.3.5 of the
manual

callback(caml_get_public_method(foo, hash_variant("bar")), foo);

Is there a better way to implement this on the OCaml side?

    Thanks, Joel

--------------------------------------------------------------------------
Working on AlgoKit, a new algorithmic trading platform using Rithmic R|API
---------------------+------------+---------------------------------------
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