On Fri, 5 Aug 2005, John Chambers wrote:
> Paul Roebuck wrote:
>
> > Can someone explain what the problem is when I use the
> > generating function? And how to get debug() to stop in
> > the Superclass initialize method?
> > [SNIP code & output]
>
> Now, the specific example. There are 3 special features used:
> 1. Nonstandard arguments for the initialize method (its official
> arguments are (.Object, ...))
>
> 2. callNextMethod
>
> 3. within callNextMethod, providing explicit arguments. The simple case
> is callNextMethod(), which passes on the arguments to the current method.
>
> Turns out that it's the third step that finds a bug in the heuristics
> used by callNextMethod to construct the actual call.
>
> In your example, you don't need the explicit arguments since they just
> replicate the formal arguments to initialize(). If you omit them, the
> computation is simpler & works.
>
> The bug can probably be fixed, but until 2.2 comes out at least, you
> need to stick to the simpler callNextMethod().
> [SNIP modified code]
Thank you for your help. Unfortunately, this is a case where
posting the simplest code necessary to display the bug works
against the poster. Actual code uses external pointers but
this revision shows more of the general concept.
If I understand your description correctly, the problem is
passing both named and unnamed arguments to callNextMethod().
Can I [easily] do either of these things to avoid the bug?
1) somehow add an argument to 'dots' and invoke callNextMethod()
without arguments?
2) parse 'dots' and invoke callNextMethod() with a completely
named argument list?
------ revised source -------
setClass("Superclass",
representation(.values = "integer",
id = "character"),
contains = "VIRTUAL")
setMethod("initialize",
signature(.Object = "Superclass"),
function(.Object, .values = NULL, id = "") {
cat("initialize (Superclass)", "\n")
if (!is.null(.values)) {
cat("\t.values =", .values, "\n")
[EMAIL PROTECTED] <- .values
}
if (length(id) > 0) {
cat("\tid =", id, "\n")
[EMAIL PROTECTED] <- id
}
.Object
})
setClass("Subclass",
contains = "Superclass")
setMethod("initialize",
signature(.Object = "Subclass"),
function(.Object, count = 1, ...) {
cat("initialize (Subclass)", "\n")
dots <- list(...)
cat("\t... =");str(dots);cat("\n")
.values = integer(count)
callNextMethod(.Object, .values = .values, ...)
})
Subclass <- function(count, id = "") {
new("Subclass", count, id = id)
}
cat("*** Create class using new() ***\n")
str(new("Subclass", id = "test0"))
str(new("Subclass", count = 3, id = "test1"))
cat("*** Create class using generating function ***\n")
#trace("initialize", signature = "Subclass", browser)
str(Subclass(count = 3, id = "test2"))
----------------------------------------------------------
SIGSIG -- signature too long (core dumped)
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
