[Q] Get formal arguments of my implemented S4 method

At this point I would just due:

formals(body(method)[[2L]])

At some point we need to figure out what to do with this .local() confusion.
Agreed, definitely.  The current hack is to avoid re-matching arguments on method dispatch, so a fix would need to be fairly deep in the implementation.

But I don't think the expression above is quite right. body(method)[[2L]] is the assignment.  You need to evaluate the rhs.

Here is a function that does the same sort of thing, and returns the standard formals for the generic if this method does not have nonstandard arguments.  We should probably add a version of this function for 3.3.0, so user code doesn't have hacks around the current hack.

methodFormals <- function(f, signature = character()) {
    fdef <- getGeneric(f)
    method <- selectMethod(fdef, signature)
    genFormals <- base::formals(fdef)
    b <- body(method)
    if(is(b, "{") && is(b[[2]], "<-") && identical(b[[2]][[2]], as.name(".local"))) {
        local <- eval(b[[2]][[3]])
        if(is.function(local))
            return(formals(local))
        warning("Expected a .local assignment to be a function. Corrupted method?")
    }
    genFormals
}

On Wed, Jan 28, 2015 at 10:07 AM, Roebuck,Paul L <PLRoebuck at mdanderson.org>
wrote:

I'm attempting to reflect the information for use with corresponding
fields in GUI (in a different package), to provide default values,
argname as key for UI label lookups, etc.

So I want something much more like the formals of the implementation:

{
   "object",
   "method":             c("median", "vs", "tukey"),
   "calc.medians":       TRUE,
   "sweep.cols":         calc.medians,
   "recalc.after.sweep": sweep.cols,
   "?"
}

not those of the generic:

{
   "object",
   "?"
}

From:  Michael Lawrence <lawrence.michael at gene.com>
Date:  Wednesday, January 28, 2015 11:28 AM
To:  "Roebuck,Paul L" <PLRoebuck at mdanderson.org>
Cc:  R-devel <r-devel at r-project.org>
Subject:  Re: [Rd] [Q] Get formal arguments of my implemented S4 method

Would you please clarify your exact use case?

Thanks,
Michael

On Wed, Jan 28, 2015 at 9:02 AM, Roebuck,Paul L
<PLRoebuck at mdanderson.org> wrote:

Interrogating some (of my own) code in another package.

norm.meth <- getMethod("normalize", "MatrixLike")
message("str(norm.meth)")
str(norm.meth)

message("show(norm.meth at .Data)")
show(norm.meth at .Data)

Last show() displays this:

function (object, ...)
{
   .local <- function (object, method = c("median", "vs", "tukey"),
       calc.medians = TRUE, sweep.cols = calc.medians,
       recalc.after.sweep = sweep.cols, ...)
   {
       .do_normalize(object,
           method = match.arg(method),
           calc.medians = calc.medians,
           sweep.cols = sweep.cols,
           recalc.after.sweep = recalc.after.sweep,
           ...)
   }
   .local(object, ...)
}

Desire to be able to access formals() for the .local() function definition,
not the generic one. Have seen information desired available via "defined"
slot of returned 'MethodDefinition' object, but not using the code below.

====================

library(methods)

if (!isGeneric("normalize")) {
   ## Other packages also define this generic...
   setGeneric("normalize",
              function(object, ...) standardGeneric("normalize"))
}

setClassUnion("MatrixLike", c("matrix", "data.frame"))

.do_normalize <- function(concs,
                         method,
                         calc.medians,
                         sweep.cols,
                         recalc.after.sweep,
                         ...) {
   message("internal routine called!")
   NULL
}

setMethod("normalize", signature(object="MatrixLike"),
         function(object,
                  method=c("median", "vs", "tukey"),
                  calc.medians=TRUE,
                  sweep.cols=calc.medians,
                  recalc.after.sweep=sweep.cols,
                  ...) {

   .do_normalize <- function(object,
                           method=match.arg(method),
                           calc.medians=calc.medians,
                           sweep.cols=sweep.cols,
                           recalc.after.sweep=recalc.after.sweep,
                           ...)
}

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[Q] Get formal arguments of my implemented S4 method

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