The problem here is that the primitive for `$` does not use standard R
evaluation on its second argument, so when it is selected as the next
method the call is effectively x$name regardless of the original call.
If possible, I would avoid such cascaded calls of methods for `$`,
precisely because of the nonstandard evaluation, which makes the
interpretation of each level of the call ambiguous.
If this kind of code is needed, then the primitive method should get a
call in which the literal name is in place and the object has been
coerced suitably.
In this example, something like
> setMethod("$", "mylist", function(x, name) {
+ theName <- substitute(name)
+ expr <- substitute(xx$NAME, list(NAME = theName))
+ xx <- unclass(x)
+ eval(expr)
+ })
[1] "$"
> tl <- new("mylist")
> tl[["z"]] <- 1
> tl$z
[1] 1
On 11/10/10 4:49 AM, Vitalie S. wrote:
Dear Developers,
callNextMethods does not work with "$"
setClass("mylist", contains = "list"):
setMethod("$",
signature(x = "mylist"),
function (x, name){
cat("here:\n")
callNextMethod()
})
tl<- new("mylist")
tl[["x"]]<- 343
tl$x
#here:
#NULL
If I use callNextMethod(x=x, name=name)
this error is issued:
Error in function (classes, fdef, mtable) :
unable to find an inherited method for function "addNextMethod", for signature
"function"
It must be something "$" specific. If the above is an expected behavior , how
should I call next method for "$" generic?
My info:
R version 2.12.0 Patched (2010-11-01 r53513)
Platform: i386-pc-mingw32/i386 (32-bit)
Same behavior for official R 2.12.0.
Thanks,
Vitalie.
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