CODEWITHSUNDEEP
c++rrcpp
Richard Redding
Richard Redding

Reputation: 327

Accessing c++ object data members from R

Apologies if this is a silly question as I am not a c++ or Rcpp expert but is it possible to access c++ data members from R? My attempt below fails:

test.cpp

#include <Rcpp.h>
using namespace Rcpp;

class myclass {
private:
  int k;
public:
  myclass(int &n) : k(n){}
  int getk() const {return k;}
};

typedef myclass* pmyclass;

// [[Rcpp::export]]
XPtr<pmyclass> new_myclass(NumericVector n_) {
  int n = as<int>(n_);
  myclass x(n);
  return(XPtr<pmyclass>(new pmyclass(&x)));
}

// [[Rcpp::export]]
NumericVector getk(SEXP xpsexp){
  XPtr<pmyclass> xp(xpsexp);
  pmyclass x = *xp;
  return wrap(x -> getk());
}

test.R

library(Rcpp)

sourceCpp('./cpp_attempt/live_in_cpp/minimal_fail/test.cpp')

ptr <- new_myclass(10)

getk(ptr)
#19274768

Upvotes: 2

Views: 267

Answers (1)

F. Priv&#233;
F. Priv&#233;

Reputation: 11728

I would use

#include <Rcpp.h>
using namespace Rcpp;

class myclass {
private:
  int k;
public:
  myclass(int n) : k(n){}
  int getk() const {return k;}
};

// [[Rcpp::export]]
SEXP new_myclass(int n) {
  XPtr<myclass> ptr(new myclass(n), true);
  return ptr;
}

// [[Rcpp::export]]
int getk(SEXP xpsexp){
  XPtr<myclass> xp(xpsexp);
  return xp->getk();
}

Upvotes: 2

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