[Rcpp-devel] Rcpp modules: Derived class - exposing method from base class?

[Jonas Rauch]

Hi Romain,

glad to hear that! Although I solved my original problem with the workaround
described, I would be happy to do some testing when you have a solution.

On Fri, Jul 8, 2011 at 2:00 PM, Romain Francois <romain at r-enthusiasts.com>wrote:

> Le 07/07/11 15:18, Romain Francois a écrit :
>
>  Le 15/06/11 14:57, Douglas Bates a écrit :
>>
>>> On Wed, Jun 15, 2011 at 6:38 AM, Jonas
>>> Rauch<jonas.rauch at googlemail.**com <jonas.rauch at googlemail.com>> wrote:
>>>
>>>> Hey again,
>>>>
>>>> just to clarify: The final solution was to implement all methods of the
>>>> derived class that are to be exposed to R and to call the method of
>>>> the base
>>>> class explicitly:
>>>>
>>>> class Bar : public Foo {
>>>> ...
>>>> void doSomething() { Foo::doSomething() }
>>>> };
>>>>
>>>
>>> Yes, we've been there before. According to Romain, it would be very
>>> tricky to expose the method of the underlying class through the
>>> derived class but it has been done in module bindings in Python, on
>>> which Romain patterned some of the Rcpp modules code.
>>>
>>
>> It is just that I need time to steal that from Boost.Python.
>>
>> This is one of the improvements I want to do in modules.
>>
>
> This is now on a background thread in my head so that I can have
> dreams/nightmares about it. I failed a few times yesterday evening and this
> morning, but I can feel I'm getting closer to at least know how to do it.
>
>
>  On Wed, Jun 15, 2011 at 7:16 AM, Jonas Rauch<jonas.rauch at googlemail.**com<jonas.rauch at googlemail.com>
>>>> >
>>>> wrote:
>>>>
>>>>>
>>>>> Actually, having just the declaration like this compiled fine but and
>>>>> ended up in an unresolved symbol when loading the library.
>>>>>
>>>>> class Bar : public Foo {
>>>>> ...
>>>>> void doSomething();
>>>>> void Action() {
>>>>> [some code here]
>>>>> }
>>>>> };
>>>>>
>>>>>
>>>>>
>>>>> I actually had to implement doSomething and explicitly call the
>>>>> Method of
>>>>> the Base class:
>>>>>
>>>>> class Bar : public Foo {
>>>>> ...
>>>>> void doSomething() { Foo::doSomething() }
>>>>> void Action() {
>>>>> [some code here]
>>>>> }
>>>>> };
>>>>>
>>>>>
>>>>> Since I do not know the internals of Rcpp modules: how hard would it
>>>>> be to
>>>>> include support for derived classes?
>>>>>
>>>>> Best regards,
>>>>> Jonas
>>>>>
>>>>> On Tue, Jun 14, 2011 at 7:36 PM, Dirk Eddelbuettel<edd at debian.org>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> Hi Jonas,
>>>>>>
>>>>>> On 14 June 2011 at 19:06, Jonas Rauch wrote:
>>>>>> | I am trying to write an R interface to a library that uses derived
>>>>>> classes in
>>>>>> | the following manner:
>>>>>> |
>>>>>> | class Foo {
>>>>>> | ...
>>>>>> | virtual void Action() = 0;
>>>>>> | void doSomething() {
>>>>>> | Action();
>>>>>> | [do complicated stuff]
>>>>>> | }
>>>>>> | ...
>>>>>> | };
>>>>>> |
>>>>>> | class Bar : public Foo {
>>>>>> | ...
>>>>>> | void Action() {
>>>>>> | [some code here]
>>>>>> | }
>>>>>> | };
>>>>>> |
>>>>>> | class Baz : public Foo {
>>>>>> | ...
>>>>>> | void Action() {
>>>>>> | [some other code here]
>>>>>> | }
>>>>>> | };
>>>>>> |
>>>>>> | etc.
>>>>>> |
>>>>>> | Where the abstract class Foo defines an interface and at the same
>>>>>> time
>>>>>> provides
>>>>>> | base functionality that can then be applied to different
>>>>>> implementations of
>>>>>> | "Action".
>>>>>> |
>>>>>> | Is it possible to expose Bar::doSomething() to R using Rcpp
>>>>>> modules? I
>>>>>> have
>>>>>> | tried different things and did not get it to work.
>>>>>>
>>>>>> Nice C++ design. And it should work, but I think your only choice
>>>>>> really
>>>>>> is
>>>>>> list all exposed functions, ie your need an explicit mention of
>>>>>> Bar::doSomething as well as Baz::doSomething. That way Rcpp Modules
>>>>>> doesn't
>>>>>> even know these are derived class. It just seens two identifiers to
>>>>>> hook
>>>>>> up
>>>>>> against. As always, I may be missing parts of the picture in which
>>>>>> case
>>>>>> Romain may come forward and correct the record....
>>>>>>
>>>>>> |
>>>>>> | I would appreciate any help.
>>>>>> |
>>>>>> | Best regards,
>>>>>> | Jonas Rauch
>>>>>> |
>>>>>> |
>>>>>> ------------------------------**------------------------------**
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>>>>>>
>>>>>>
>>>>>> --
>>>>>> Gauss once played himself in a zero-sum game and won $50.
>>>>>> -- #11 at http://www.gaussfacts.com
>>>>>>
>>>>>
>>>>>
>>>>
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>>
>>
>
> --
> Romain Francois
> Professional R Enthusiast
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