* On 2008-09-17 at 19:25 -0700 Seth Falcon wrote:
> In the latest R-devel code (svn r46542), this behaves differently (and
> works as you were hoping). I get:
>
> library("RSQLite")
> setClass("SQLConPlus", contains=c("SQLiteConnection","integer"))
> dd = data.frame(a=1:3, b=letters[1:3])
> con = new("SQLConPlus", dbConnect(SQLite(), ":memory:"), 11L)
> dbWriteTable(con, "t1", dd)
> dbListTables(con)
> dbDisconnect(con)
*argh* I'm certain this was working for me and yet when I try to
reproduce in a new R shell it errors out. The dispatch is not as I
wrote.
as(con, "integer")
[1] 11
That is, the auto-generated coerce method to integer is selected in
preference to the coerce method for SQLiteConnection.
> I think the new behavior is desirable as it follows the rule that the
> order of the superclasses listed in contains is used to break ties
> when multiple methods match. Here, there are two coerce() methods
> (invoked via as()) one for SQLiteConnection and one, I believe
> auto-generated, for integer. Since SQLiteConnection comes first, it
> is chosen. Indeed, if you try the following, you get the error you
> were originally seeing:
>
> setClass("SQLConMinus", contains=c("integer", "SQLiteConnection"))
> con2 = new("SQLConMinus", dbConnect(SQLite(), ":memory:"), 11L)
>
> > as(con, "integer")
> [1] 15395 2
> > as(con2, "integer")
> [1] 11
> >
I'm still baffled how this was working for me and now is not.
Nevertheless, I think it is how things *should* work and will do some
further investigation about what's going on.
--
Seth Falcon | http://userprimary.net/user/
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