How to patch an S4 method in an R package?

If you find a bug in a package, it's usually possible to patch the problem with fixInNamespace, e.g. fixInNamespace("mean.default", "base").

For S4 methods, I'm not sure how 开发者_开发问答to do it though. The method I'm looking at is in the gWidgetstcltk package. You can see the source code with

getMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"))

I can't find the methods with fixInNamespace.

fixInNamespace(".svalue", "gWidgetstcltk")

Error in get(subx, envir = ns, inherits = FALSE) : 
  object '.svalue' not found

I thought setMethod might do the trick, but

setMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"),
  definition = function (obj, toolkit, index = NULL, drop = NULL, ...) 
  {
      widget = getWidget(obj)
      sel <- unlist(strsplit(tclvalue(tcl(widget, "selection")), 
          " "))
      if (length(sel) == 0) {
          return(NA)
      }
      theChildren <- .allChildren(widget)
      indices <- sapply(sel, function(i) match(i, theChildren))
      inds <- which(visible(obj))[indices]
      if (!is.null(index) && index == TRUE) {
          return(inds)
      }
      if (missing(drop) || is.null(drop)) 
          drop = TRUE
      chosencol <- tag(obj, "chosencol")
      if (drop) 
          return(obj[inds, chosencol, drop = drop])
      else return(obj[inds, ])
  },
  where = "package:gWidgetstcltk"  
)

Error in setMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"),  : 
  the environment "gWidgetstcltk" is locked; cannot assign methods for function ".svalue"

Any ideas?

---

How about the old-school way of getting the source, applying the change and rebuilding?

---

you can first get the generic out, and then fix the generic by setMethod in your global environment, and then assign it back to that namespace

.svalue <- gWidgetstcltk:::.svalue
setMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"),
  definition = function (obj, toolkit, index = NULL, drop = NULL, ...) 
  {
      widget = getWidget(obj)
      sel <- unlist(strsplit(tclvalue(tcl(widget, "selection")), 
          " "))
      if (length(sel) == 0) {
          return(NA)
      }
      theChildren <- .allChildren(widget)
      indices <- sapply(sel, function(i) match(i, theChildren))
      inds <- which(visible(obj))[indices]
      if (!is.null(index) && index == TRUE) {
          return(inds)
      }
      if (missing(drop) || is.null(drop)) 
          drop = TRUE
      chosencol <- tag(obj, "chosencol")
      if (drop) 
          return(obj[inds, chosencol, drop = drop])
      else return(obj[inds, ])
  }#,
  #where = "package:gWidgetstcltk"  
)
assignInNamespace(".svalue", .svalue, ns = "gWidgetstcltk")