R help - Sep 2013 - callNextMethod with dots argument

Hi,

I met a problem when invoking callNextMethod within a method associated 
with a generic function taking ... as an argument.

Here is the code

setClass("Aparent",representation(x="numeric",y="numeric"))
setClass("Achild",contains="Aparent")

setGeneric("do",def=function(a,...) standardGeneric("do"))
setMethod("do",signature(a="Aparent"),
           function(a,msg) {
             print("do Aparent")
           })
setMethod("do",signature(a="Achild"),
           function(a,msg)  {
             print("do Achild")
             callNextMethod()
           })

myA <- new("Achild")
buf <- do(a=myA)               # works
buf <- do(a=myA,msg="bonjour") # error

The last call yields the following error message:

Error in callNextMethod() :
   in processing 'callNextMethod', found a '...' in the matched
call,
but no corresponding '...' argument

which I do not understand. Replacing "..." by "msg" in
setGeneric makes
it work. But I don't like this limitation so much (unless I understand it).

Regards.

Kien

Kien,

if you want to add variables in a function definition that is predefined by a
Generic and calls CallNextMethod you have to add the '?' argument as
well.
> setMethod("do",signature(a="Achild"),
>          function(a,msg,...)  {
>            print("do Achild")
>            callNextMethod()
>          })
Best

Simon

On Sep 19, 2013, at 8:58 AM, Ki?n Ki?u <kien.kieu at jouy.inra.fr> wrote:
> Hi,
> 
> I met a problem when invoking callNextMethod within a method associated
with a generic function taking ... as an argument.
> 
> Here is the code
> 
>
setClass("Aparent",representation(x="numeric",y="numeric"))
> setClass("Achild",contains="Aparent")
> 
> setGeneric("do",def=function(a,...)
standardGeneric("do"))
> setMethod("do",signature(a="Aparent"),
>          function(a,msg) {
>            print("do Aparent")
>          })
> setMethod("do",signature(a="Achild"),
>          function(a,msg)  {
>            print("do Achild")
>            callNextMethod()
>          })
> 
> myA <- new("Achild")
> buf <- do(a=myA)               # works
> buf <- do(a=myA,msg="bonjour") # error
> 
> The last call yields the following error message:
> 
> Error in callNextMethod() :
>  in processing 'callNextMethod', found a '...' in the
matched call, but no corresponding '...' argument
> 
> which I do not understand. Replacing "..." by "msg" in
setGeneric makes it work. But I don't like this limitation so much (unless I
understand it).
> 
> Regards.
> 
> Kien
> 
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