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Martin Morgan wrote:
> Hi Ross --
>
> Ross Boylan <r...@biostat.ucsf.edu> writes:
>
>> I have classes A and B, where B contains A. In the implementation of
>> the group generic for B I would like to use the corresponding group
>> generic for A. Is there a way to do that?
>> setMethod("Arith", signature(e1="numeric", e2="B"), function(e1, e2) {
>> # the next line does not work right
>> v <- selectMethod("callGeneric", signature=c("numeric", "A"))(e1, e2)
>
> v <- callGeneric(e1, as(e2, "A"))
>
> or probably
>
> v <- callNextMethod(e1, e2)
>
> Martin
A different error this time, one that looks a lot like the report from
stephen.p...@ubs.com on 2007-12-24 concerning callNextMethod:, except
this is with
callGeneric.
HOWEVER, the problem is erratic; when I started from scratch and took
this code into a workspace and executed the commands, they worked as
expected. I had various false starts and revisions, as well as the real
code on which the example is based, when the error occurred. I tried
taking in the real code (which defines generics with Arith from my
actual classes, and which also fails as below), and the example still
worked.
My revised code:
setClass("A",
representation=representation(xa="numeric")
)
setMethod("Arith", signature(e1="numeric", e2="A"), function(e1, e2) {
new("A", xa=callGeneric(e1, e...@xa))
}
)
setClass("B",
representation=representation(xb="numeric"),
contains=c("A")
)
setMethod("Arith", signature(e1="numeric", e2="B"), function(e1, e2) {
new("B", xb=e1...@xb, callNextMethod())
}
)
Results:
> options(error=recover)
> tb <- new("B", xb=1:3, new("A", xa=10))
> 3*tb
Error in get(fname, envir = envir) : object '.nextMethod' not found
Enter a frame number, or 0 to exit
1: 3 * tb
2: 3 * tb
3: test.R#16: new("B", xb = e1 * e...@xb, callNextMethod())
4: initialize(value, ...)
5: initialize(value, ...)
6: callNextMethod()
7: .nextMethod(e1 = e1, e2 = e2)
8: test.R#6: new("A", xa = callGeneric(e1, e...@xa))
9: initialize(value, ...)
10: initialize(value, ...)
11: callGeneric(e1, e...@xa)
12: get(fname, envir = envir)
Selection: 0
The callGeneric in frame 11 is trying to get the primitive for
multiplying numeric times numeric. Quoting from Pope's analysis:
[The primitive...]
> does not get the various "magic" variables such as .Generic, .Method,
> etc. defined in its frame. Thus, callGeneric() fails when, failing to
> find ".Generic" then takes the function symbol for the call (which
> callNextMethod() has constructed to be ".nextMethod") and attempts to
> look it up, which of course also fails, leading to the resulting error
> seen above.
I'm baffled, and hoping someone on the list has an idea.
I'm running R 2.10 under ESS (in particular, I use c-c c-l in the code
file to read in the code) on XP.
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