[R-pkg-devel] Define S4 method for generic in other package

[Hadley Wickham]

I'd recommend creating a minimal package that illustrates the problem
using an existing S4 generic in a base package (e.g. stats4::AIC).
That makes it easier to figure out what's gone wrong.

It's unlikely to be a roxygen2 problem since the translation from
@importFrom foo bar (etc) to importFrom(foo, bar) is quite
straightforward.

Hadley

On Fri, Aug 28, 2015 at 3:23 AM, Thierry Onkelinx
<thierry.onkelinx at inbo.be> wrote:
> Dear all,
>
> I'm trying to define a new S4 method for a generics defined in an
> other package. Here is my attempt, but that isn't working.
>
> bar <- function(a, b) is defined as generic and S4 method in the package foo
>
> #' @importFrom foo bar
> #' @importMethodsFrom foo bar
> setMethod(
>   f = "bar",
>   signature = signature(A = "myClass"),
>   definition = function(
>     a,
>     b
>   ){
>     bar(
>       a = myClass at A,
>       b = myClass at B
>     )
>   }
> )
>
> When I build my package I get the error "no existing definition for
> function 'bar'".
>
> Any suggestions?
>
> Best regards,
>
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature
> and Forest
> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> Kliniekstraat 25
> 1070 Anderlecht
> Belgium
>
> To call in the statistician after the experiment is done may be no
> more than asking him to perform a post-mortem examination: he may be
> able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher
> The plural of anecdote is not data. ~ Roger Brinner
> The combination of some data and an aching desire for an answer does
> not ensure that a reasonable answer can be extracted from a given body
> of data. ~ John Tukey
>
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