[Rcpp-devel] wrap returned pointer to class

[Dirk Eddelbuettel]

Sebastuan,

On 1 August 2011 at 18:07, Sebastian Weber wrote:
| first of all thank you, Dirk and Romain, so much for this great library! I was stunned when I saw the examples.
| 
| Hence, I started immediately a quite involved project which interfaces another library to R via C++. 

That should work.  The number of packages on CRAN which use Rcpp just that
keeps increasing -- we added a few more last week -- and several of those
interface external libraries or code.

| Currently I have the problem that I want to expose a function from a class which returns a pointer to a class. When exposing via the
| 
| class_<A>.method("fun", &A::fun);
| 
| mechanism, the compiler fails with a message saying that he cannot wrap the return type of function fun. The returned object itself is a pointer to another class B. How to solve this? I tried providing the wrap call with no success.
| 
| Here is some code which might not work, but explains more detailed:
| 
| class B {};
| 
| class A {
| public:
| 	B* fun();
| };
| 
| which gives, when compiled:
| 
| /Library/Frameworks/R.framework/Versions/2.13/Resources/library/Rcpp/include/Rcpp/internal/wrap.h:428: error: cannot convert ‘B* const’ to ‘SEXPREC*’ in initialization
| 
| Any ideas how to fix this?

It seems to me that the issue is not so much that you have a pointer to B, as
it is that Rcpp simply does not what B is -- in the sense of having wrap()
and as<> operators for objects of class "B".  

You would have to provide those, see the Rcpp-package vignette.
 
| Thanks,
| 
| PS: Is there some bug tracking tool? I got some weird problem when the function wrapped expects a char as input. I fixed it somehow, but I am not sure if it is the right way...

Not really. The R-Forge project site has it, but the reports there get mostly
ignored / forgotten.  The best idea is to post a reproducible example of some
exciting bug here.  To more exciting the bug the higher the chance it will
get addressed :)

Cheers, Dirk

 
| -- 
| Sebastian Weber
| Group of Cell Communication and Control
| Freiburg Institute for Advanced Studies - FRIAS
| School of Life Sciences - LIFENET
| Albert-Ludwigs-Universität Freiburg
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