I have encountered an issue which I have been unable to resolve, involving
an S3 generic (print) being declared S4 generic in a package, and the method
being exported. This all works fine - the problem occurs when I try to
import the method to another package.
Here is the bit that works fine. -------------
#the .r file for package bar
setClass("bar",representation("numeric"))
if(!isGeneric("print")) {setGeneric("print",useAsDefault=print)}
setMethod("print",signature(x="bar"),
print.bar <- function(x,...)
{
print("print method for bar")
print([EMAIL PROTECTED],...)
}
)
if(!isGeneric("barprint")) {setGeneric("barprint",useAsDefault=print)}
setMethod("barprint",signature(x="bar"),
printBar <- function(x,...)
{
print("barprint method for bar")
print([EMAIL PROTECTED],...)
}
)
#the NAMESPACE file for package bar
import(methods)
exportMethods(barprint,print)
exportClasses("bar")
#then in R:
> require(barpkg)
Loading required package: barpkg
[1] TRUE
> x <- new("bar",99)
> print(x)
[1] "print method for bar"
[1] 99
> barprint(x)
[1] "barprint method for bar"
[1] 99
Fine.
Here is the bit that I have not figured out. -------------
#the .r file for package waz
wazbar <- function(x)
{
barprint(new("bar",x))
}
#the NAMESPACE file for package waz
import(methods,barpkg)
importMethodsFrom(barpkg)
importClassesFrom(barpkg)
export(wazbar)
#then in R
> require(wazpkg)
Loading required package: wazpkg
[1] TRUE
> wazbar(99)
Error in .setMethodsForDispatch(f, fdef, resetMlist) :
Internal error: did not get a valid generic function object for
function "print"
Error in print("barprint method for bar") :
S language method selection got an error when called from internal
dispatch for function "print"
end of R bit ---------------------------
The problem goes away if I don't set print as an S4 generic in bar.
Can anyone help - maybe an error is obvious?
As a bit of background, I am package maintainer for its (Irregular
Time-Series), and have been obliged to put it in a namespace or suffer a
significant performance penalty (about 6x slower). In the package I make S3
generics (plot, print, summary etc) S4 generic in this package, and so far
have not got into trouble for doing so. However, I have now got stuck -
possibly I have not seen the right documentation (I refer to the newsletter
article, and John Chambers' correspondence on R-devel early September).
- Giles
platform i386-pc-mingw32
arch i386
os mingw32
system i386, mingw32
status
major 1
minor 8.1
year 2003
month 11
day 21
language R
Rcmd install --doc="none" barpkg
**********************************************************************
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