[R] own TAB expansion

[Deepayan Sarkar]

On Fri, Oct 8, 2010 at 6:19 AM, Sebastian Gibb <lists at sebastiangibb.de> wrote:
> Hello Duncan,
>
> thank for your advice, but it doesn't work like expected:
>
> setClass(Class="A", representation=representation(slotA="numeric",
> slotB="numeric"));
> setMethod("$", "A", function(x, name) {return(slot(x, name));})
> setGeneric(".DollarNames")
> setMethod(".DollarNames", signature(x="A"), function(x,
> pattern)grep(pattern=pattern, x=c("slotA", "slotB"), value=T))
>
> a <- new("A", slotA=1, slotB=2)
> a$sl  <TAB>
> # doesn't print slotA/slotB
>> a$
>
> What I'm doing wrong?

There is a namespace issue with making .DollarNames() generic;
basically, the completion code in the utils namespace never sees the
new S4 generic. See a previous discussion at

http://www.mail-archive.com/r-devel@r-project.org/msg20553.html

Defining a S3 method should work (without the need for a dummy S3
class even with inheritance if you are working with R 2.12):

.DollarNames.A <-
    function(x, pattern) {
        grep(pattern=pattern, x=c("slotA", "slotB"), value=T)
    }

-Deepayan