dump(<S7_object>)?

[HenrikBengtsson]

I'm late to the party, and sorry if I missed a discussion on this, but is there a way to dump() an S7 object? Attempting to do so gives:

> x <- S7::S7_object()
> dump("x", file = stdout())
x <-
<object>
Warning message:
In dump("x", file = stdout()) : deparse may be incomplete

which is not valid R code.

Ultimately, I want to create a minimal, valid S7_object object without using the 'S7' package. I want this in order to write a teeny 'codetools'-related unit test, without having to depend on the 'S7' package. Thus far, I know I can save an S7_object object to an RDS file, and obtain such a "creature" without having the 'S7' package installed, e.g.

> z <- readRDS("s7.rds")
> z
<object>
attr(,"class")
[1] "S7_object"

but it would be nice not to rely on a binary representation for my unit tests.

[t-kalinowski]

The return value from S7_object() is a OBJSXP (formerly known as S4SXP), but with the S4 bit unset. For a time I thought it was only possible to make this object from C.

However, @ltierney did find a way to make it in R at some point:

mkObj <- function(...) {
  ob <- asS3(getClass("S4")@prototype, complete = FALSE) # "hack"
  if (...length())
    attributes(ob) <- list(...)
  ob
}


identical(mkObj(class = "S7_object"), S7::S7_object())
#> [1] TRUE

This doesn't solve the need for better serialization support, but hopefully it unblocks you.

[t-kalinowski]

Supporting dput() or equivalent would be very help for the next release.

[hadley]

Proof of concept in r-devel/r-svn#263