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")