How do I check if an externalptr is NULL from within R

Question

I\'m using SWIG to generate wrapper code to access C code from within the R language. The wrapper code uses the R externalptr type to hold references to C pointers

Answer 1

The C solution above is most elegant, but a compiler might not always be available. A solution that does not require compiled code could be something like:

identical(pointer, new("externalptr"))

However this would not work if the object has custom attributes. If this is the case, you could do:

isnull <- function(pointer){
  a <- attributes(pointer)
  attributes(pointer) <- NULL
  out <- identical(pointer, new("externalptr"))
  attributes(pointer) <- a
  return(out)
}

Again a bit more involved than the C solution, but will work in a simple script on any platform.