S4 dispatch for .DollarNames (utils)

Hello,

I'm trying to make .DollarNames generic and implement a method for it in
a package. .DollarNames is the function that is now called to get
completion possibilities.

My R code looks like this:

setGeneric( ".DollarNames" )

setClass("track",
representation(x="numeric", y="numeric"))
## A class extending the previous, adding one more slot
setClass("trackCurve",
representation(smooth = "numeric"),
contains = "track")

setMethod( ".DollarNames", signature( x = "track", pattern = "character"
), function(x, pattern){
grep( pattern, c("foo", "bar"), value = TRUE )
} )


and the NAMESPACE :

import( utils )
exportMethods( .DollarNames )
exportClasses( track, trackCurve )


When I load the package, I can call .DollarNames explicitely :

 > require( foo )
 > x <- new( "trackCurve", x = 1:10, y = 1:10, smooth = 1:10 )
 > .DollarNames( x, "f" )

[1] "foo"

but completion does not work :

 > x$f<TAB>

x$


What do I miss ?

I've uploaded foo here :
http://addictedtor.free.fr/misc/rcpp/foo_1.0.tar.gz

Romain

Hello,

I'm trying to make .DollarNames generic and implement a method for it in a
package. .DollarNames is the function that is now called to get completion
possibilities.

My R code looks like this:

setGeneric( ".DollarNames" )

setClass("track",
? ? ? ? representation(x="numeric", y="numeric"))
## A class extending the previous, adding one more slot
setClass("trackCurve",
? ?representation(smooth = "numeric"),
? ?contains = "track")

setMethod( ".DollarNames", signature( x = "track", pattern = "character" ),
function(x, pattern){
? ? ? ?grep( pattern, c("foo", "bar"), value = TRUE )
} )


and the NAMESPACE :

import( utils )
exportMethods( .DollarNames )
exportClasses( track, trackCurve )


When I load the package, I can call .DollarNames explicitely :

require( foo )
x <- new( "trackCurve", x = 1:10, y = 1:10, smooth = 1:10 )
.DollarNames( x, "f" )

[1] "foo"

but completion does not work :

x$f<TAB>

x$

utils:::.DollarNames(x, "f")

What do I miss ?

I've uploaded foo here : http://addictedtor.free.fr/misc/rcpp/foo_1.0.tar.gz

Romain


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Professional R Enthusiast
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On Sat, May 29, 2010 at 4:21 AM, Romain Francois
<romain at r-enthusiasts.com>  wrote:

Hello,

I'm trying to make .DollarNames generic and implement a method for it in a
package. .DollarNames is the function that is now called to get completion
possibilities.

My R code looks like this:

setGeneric( ".DollarNames" )

setClass("track",
         representation(x="numeric", y="numeric"))
## A class extending the previous, adding one more slot
setClass("trackCurve",
    representation(smooth = "numeric"),
    contains = "track")

setMethod( ".DollarNames", signature( x = "track", pattern = "character" ),
function(x, pattern){
        grep( pattern, c("foo", "bar"), value = TRUE )
} )


and the NAMESPACE :

import( utils )
exportMethods( .DollarNames )
exportClasses( track, trackCurve )


When I load the package, I can call .DollarNames explicitely :

require( foo )
x<- new( "trackCurve", x = 1:10, y = 1:10, smooth = 1:10 )
.DollarNames( x, "f" )

[1] "foo"

but completion does not work :

x$f<TAB>

x$

I guess because

utils:::.DollarNames(x, "f")

character(0)

so the S4 generic is not being seen within the utils namespace. I
don't know what the right fix is...

-Deepayan

What do I miss ?

I've uploaded foo here : http://addictedtor.free.fr/misc/rcpp/foo_1.0.tar.gz

Romain

The workaround/hack that *does* work now, I believe, is to insert a 
dummy S3 class into the mix and define the S3 .DollarNames method for it.

Example:

 > setOldClass("foo3")
 > .DollarNames.foo3 <- function(x, pattern)"bar"

Dear all,

thank your for this discussion - I had been wondering how to get the 
completion with my S4 class, but it didn't bother me enough to dig 
into things.

The workaround/hack that *does* work now, I believe, is to insert a 
dummy S3 class into the mix and define the S3 .DollarNames method for 
it.

Example:

setOldClass("foo3")
.DollarNames.foo3 <- function(x, pattern)"bar"

My question here is: what is the dummy class needed for?

I have a few S3 methods for my S4 class (rbind.hyperSpec, 
cbind.hyperSpec, and now .DollarNames.hyperSpec). They seem to work 
just fine without first setting up a dummy S3 class that is then used 
in the contains of the S4 definition.
Any pitfalls with that?

Claudia