Re: [R] accesing slots of S4 class in C code

From: Duncan Temple Lang <duncan_at_wald.ucdavis.edu>
Date: Thu 18 Aug 2005 - 04:29:15 EST

You need to use .Call() rather than .C() to pass the R object to the TestFun routine.

 D.

Aniko Szabo wrote:
> I am trying to use a custom S4 object in my C code and I cannot get the
> access to its slots working.
>
>
>
> The following is a toy example, but even this crashes.
>
>
>
> In R I have:
>
>
>
> setClass("pd", representation(data="numeric"))
>
> x <- new("pd", data=1:5)
>
>
>
> test <- function(pd.obj) {
>
> res <- .C("TestFun", pd.obj)
>
> res}
>
>
>
> test(x)
>
>
>
> (Of couse I load the DLL as well.)
>
>
>
> The corresponding C file has:
>
>
>
> SEXP TestFun(SEXP pd_obj)
>
> {
>
> SEXP t=R_NilValue;
>
> PROTECT(t = GET_SLOT(pd_obj, install("data")));
>
> UNPROTECT(1);
>
> return(t);
>
> }
>
>
>
>
>
> What I hope to get as a result is the (1:5) vector.
>
> In the long term, the vector will be a multi-dimensional array and I
> will want to do calculations using its contents in the C program.
>
>
>
> Thanks for any help,
>
>
>
> Aniko
>
>
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>
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-- 
Duncan Temple Lang                duncan@wald.ucdavis.edu
Department of Statistics          work:  (530) 752-4782
371 Kerr Hall                     fax:   (530) 752-7099
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University of California at Davis
Davis, CA 95616, USA




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