Thanks, Sebastian, for the pointer to the NEWS item. After some further search, I also found this in the R Blog:
https://developer.r-project.org/Blog/public/2019/08/19/s3-method-lookup/ Best, Wolfgang >-----Original Message----- >From: R-devel [mailto:r-devel-boun...@r-project.org] On Behalf Of Sebastian >Meyer >Sent: Tuesday, 12 May, 2020 21:17 >To: r-devel@r-project.org >Subject: Re: [Rd] S3 method dispatch for methods in local environments > >Dear Wolfgang, > >I think this new behaviour is related to the following R 4.0.0 NEWS item: > >> S3 method lookup now by default skips the elements of the search path >between the global and base environments. > >Your environment "myenv" is attached at position 2 of the search() path >and thus now skipped in S3 method lookup. > >I have just noticed that > >attr(methods(class="myclass"), "info") >getS3method("print", "myclass") > >both still find your function in myenv although the generic's >UseMethod() won't. I find this a bit confusing. > >A solution to make R >= 4.0.0 find your method is to register the S3 >method using the new function .S3method (intended for R scripts, not >packages). After running > >.S3method("print", "myclass", myenv$print.myclass) > >your method will be found from the generic. > >Best regards, > > Sebastian > > >Am 12.05.20 um 20:05 schrieb Viechtbauer, Wolfgang (SP): >> Dear All, >> >> In R 3.6.3 (and earlier), method dispatch used to work for methods stored >in local environments that are attached to the search path. For example: >> >> myfun <- function(y) { >> out <- list(y=y) >> class(out) <- "myclass" >> return(out) >> } >> >> print.myclass <- function(x, ...) print(formatC(x$y, format="f", >digits=5)) >> >> myfun(1:4) >> >> # prints: [1] "1.00000" "2.00000" "3.00000" "4.00000" >> >> rm(print.myclass) >> myenv <- new.env() >> myenv$print.myclass <- local(function(x, ...) print(formatC(x$y, >format="f", digits=5)), myenv) >> attach(myenv) >> myfun(1:4) >> >> # still prints: [1] "1.00000" "2.00000" "3.00000" "4.00000" >> >> But since R 4.0.0, this no longer words and the above prints: >> >> $y >> [1] 1 2 3 4 >> >> attr(,"class") >> [1] "myclass" >> >> Is this intended? And is there a way to still make this work? >> >> Best, >> Wolfgang ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
