Le 13/04/10 00:14, Douglas Bates a écrit :
One of the advantages of using S4 classes and methods in R is that
there are formal definitions of classes. I plan eventually to write R
code that will take an S4 class definition and create a C++ class
definition and constructor code to mirror the R class using Rcpp
templates.
Right now my question is related to constructors. If I have a slot in
an S4 class that is itself an S4 object, is there a way to chain the
constructor so that I generate the internal object without first
creating an empty object.
To be specific, I have an S4 class "reModule" that contains sparse
matrices of S4 class "dgCMatrix" and some information that is atomic.
The S4 definition is (more-or-less)
setClass("reModule", representation(Lambda = "dgCMatrix", Zt =
"dgCMatrix", theta = "numeric", Lind = "integer"))
and the definition of dgCMatrix is
setClass("dgCMatrix", representation(Dim = "integer", i = "integer", p
= "integer", x = "numeric")
Using Rcpp I define C++ classes
class dgCMatrix {
public:
dgCMatrix(Rcpp::S4);
Rcpp::IntegerVector Dim, i, p;
Rcpp::NumericVector x;
};
class reModule {
public:
reModule(Rcpp::S4);
dgCMatrix Lambda, Zt;
Rcpp::NumericVector theta;
Rcpp::IntegerVector Lind;
};
If I define a constructor for the reModule without chaining to
constructors for the dgCMatrix objects then I need to define a
dgCMatrix::dgCMatrix() constructor and then redefine the Lambda and Zt
members inside the reModule constructor. I think a more idiomatic C++
constructor definition is to chain to the other constructor as in
using namespace Rcpp;
reModule::reModule(S4 xp) :
Lambda(S4(xp.slot("Lambda"))),
Zt(S4(xp.slot("Zt"))),
...
{
}
but the compiler doesn't like constructing an S4 object from an
Rcpp::RObject::SlotProxy.
It should work now (rev 1171).
Can I ask you to add an unit test in runit.S4.R for this.
The way I have gotten around this is to use
Lambda(S4(SEXP(xp.slot("Lambda"))))
etc.
Is that a reasonable construction to use?
--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
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