[omniORB] IDL for callback-object

[Stefan Seefeld]

henning.schmidt@philips.com wrote:

>I am trying to come up with an IDL for a CallbackObject with similar semantics to the VkCallbackObject. (see below)
>

That's not related to omniORB. You may want to post to comp.object.corba 
for this kind of questions.

>
>Has anyone been able to come up with something clever that is generic enough so that I don't need to know the function to be called in the IDL where I define the rest of the Framework. I don't seem to be able to find a nice way to do what a pointer to 
>object-function does in C++.
>

I don't think this is something IDL should be concerned about at all. 
Just use an abstract factory and you
should be fine:

interface Callback
{
   void execute(in Any a);
};

interface CallbackFactory
{
   Callback foo_callback();
   Callback bar_callback();
};

and then in the servant:

template <typename T>
class CallbackImpl : public virtual POA_Callback
{
   typedef void (*T::method)();
public:
   CallbackImpl(T *t, method m) : _t(t), _m(m) {}
   void execute() { (t->*m)();}
private:
   T *_t;
   method _m;
};

class CallbackFactoryImpl : public virtual POA_CallbackFactory
{
   Callback_ptr foo_callback()
    {
       Foo *foo = ...;
       CallbackImpl<Foo> *callback = new CallbackImpl<Foo>(foo, 
&foo::whatever);
       return callback->_this();
     }
   // and so on...
};

a number of variations are possible based on the same theme, passing 
parameters to the
factory methods that serve as discriminator to determine the exact 
callback to instantiate.


Regards,    Stefan