R devel - May 2015 - Define replacement functions

Hello

I tried to define replacement functions for the class "mylist". When I
test them in an active R session, they work -- however, when I put them into a
package, they don't. Why and how to fix?


make_my_list <- function( x, y ) {
	return(structure(list(x, y, class="mylist")))
}
mylist <- make_my_list(1:4, letters[3:7])
mylist
mylist[['x']] <- 4:6
mylist
"[[<-" <- function(x, field, value) {
	UseMethod('[[<-', x)
}
"[[<-.mylist" <- function(x, field, value) {
	stop( "Do not assign." )
}
mylist[['x']] <- 1:10
mylist
mylist$y <- LETTERS[1:3]
mylist
"$<-" <- function(x, field, value) {
	UseMethod('$<-', x)
}
"$<-.mylist" <- function(x, field, value) {
	stop( "Do not assign." )
}
mylist$y <- LETTERS[10:15]


Thanks for help
S?ren

Did you export the S3 methods in the NAMESPACE?

Hadley

On Mon, May 4, 2015 at 7:52 AM,  <soeren.vogel at posteo.ch>
wrote:
> Hello
>
> I tried to define replacement functions for the class "mylist".
When I test them in an active R session, they work -- however, when I put them
into a package, they don't. Why and how to fix?
>
>
> make_my_list <- function( x, y ) {
>         return(structure(list(x, y, class="mylist")))
> }
> mylist <- make_my_list(1:4, letters[3:7])
> mylist
> mylist[['x']] <- 4:6
> mylist
> "[[<-" <- function(x, field, value) {
>         UseMethod('[[<-', x)
> }
> "[[<-.mylist" <- function(x, field, value) {
>         stop( "Do not assign." )
> }
> mylist[['x']] <- 1:10
> mylist
> mylist$y <- LETTERS[1:3]
> mylist
> "$<-" <- function(x, field, value) {
>         UseMethod('$<-', x)
> }
> "$<-.mylist" <- function(x, field, value) {
>         stop( "Do not assign." )
> }
> mylist$y <- LETTERS[10:15]
>
>
> Thanks for help
> S?ren
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


-- 
http://had.co.nz/

No. I fixed that, the NAMESPACE file now contains:

S3method("[[<-", mylist)
S3method("$<-", mylist)

It still does not work. I also created a print method (print.mylist) which did
work out of the box, regardless of being in the NAMESPACE file or not. Could it
be somehow in here (also in my NAMESPACE file):

exportPattern("^[[:alpha:]]+")

Or could it be that the type of quoting causes the problems? Like in the
NAMESPACE I used double quotes for function definition. Do I need single quotes
or back-ticks?

Or is there a package where I can look how others implemented this kind of
functionality?

S?ren
> On 04.05.2015, at 16:17, Hadley Wickham <h.wickham at gmail.com>
wrote:
> 
> Did you export the S3 methods in the NAMESPACE?
> 
> Hadley
> 
> On Mon, May 4, 2015 at 7:52 AM,  <soeren.vogel at posteo.ch> wrote:
>> Hello
>> 
>> I tried to define replacement functions for the class
"mylist". When I test them in an active R session, they work --
however, when I put them into a package, they don't. Why and how to fix?
>> 
>> 
>> make_my_list <- function( x, y ) {
>>        return(structure(list(x, y, class="mylist")))
>> }
>> mylist <- make_my_list(1:4, letters[3:7])
>> mylist
>> mylist[['x']] <- 4:6
>> mylist
>> "[[<-" <- function(x, field, value) {
>>        UseMethod('[[<-', x)
>> }
>> "[[<-.mylist" <- function(x, field, value) {
>>        stop( "Do not assign." )
>> }
>> mylist[['x']] <- 1:10
>> mylist
>> mylist$y <- LETTERS[1:3]
>> mylist
>> "$<-" <- function(x, field, value) {
>>        UseMethod('$<-', x)
>> }
>> "$<-.mylist" <- function(x, field, value) {
>>        stop( "Do not assign." )
>> }
>> mylist$y <- LETTERS[10:15]
>> 
>> 
>> Thanks for help
>> S?ren
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 
> 
> -- 
> http://had.co.nz/