[R] callNextMethod with dots argument

[Simon Zehnder]

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, Kiên Kiêu <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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