S4 coercion

## class hierarchy
setClass("A", representation=representation(a="numeric"))

setClass("B", representation=representation(b="numeric"))

setClass("C", contains=c("A", "B"))

## coerce methods -- in some instances implicitly created
setAs("A", "numeric", function(from) slot(from, "a"))
setAs("B", "numeric", function(from) slot(from, "b"))

## trouble: C equidistant from A, B so no unambiguous nearest 'coerce'
## method
as(new("C"), "numeric")

I am extending a DBI connection by

setClass("TSPostgreSQLConnection",
contains=c("PostgreSQLConnection","TSdbOptions"))

but the first time I use this I am getting a warning when it tries to
coerce  the  TSPostgreSQLConnection to a PostgreSQLConnection. After
the first use the warning stops,  but the first warning is causing me
problems when I do automatic checks and set my tests to stop on
warnings. (I think there should be a correct way to do this that does
not produce a warning.)  I can trace it back by setting
options(warn=2) as below.  Do I need to be more specific about how the
coercion  happens? If so, what is the correct way to coerce the
TSPostgreSQLConnection into a PostgreSQLConnection? If not, how to a
get rid of the warning?

Paul Gilbert

 > TSdelete("vec", con)

Error: (converted from warning) Ambiguous method selection for
"coerce", target "TSPostgreSQLConnection#integer" (the first of the
signatures shown will be used)
   PostgreSQLConnection#integer
   dbObjectId#integer

 > traceback()

15: doWithOneRestart(return(expr), restart)
14: withOneRestart(expr, restarts[[1]])
13: withRestarts({
       .Internal(.signalCondition(simpleWarning(msg, call), msg,
           call))
       .Internal(.dfltWarn(msg, call))
   }, muffleWarning = function() NULL)
12: .signalSimpleWarning("Ambiguous method selection for \"coerce\",
target \"TSPostgreSQLConnection#integer\" (the first of the signatures
shown will be used)\n    PostgreSQLConnection#integer\n
dbObjectId#integer\n",
       quote(NULL))
11: warning(gettextf(paste("Ambiguous method selection for \"%s\",
target \"%s\"",
       "(the first of the signatures shown will be used)\n%s\n"),
       fdef at generic, .sigLabel(classes), paste("   ", names(methods),
           collapse = "\n")), domain = NA, call. = FALSE)
10: .findInheritedMethods(signature, fdef, mtable = allmethods, table
= mlist,
       useInherited = useInherited, verbose = verbose)
9: selectMethod("coerce", sig, optional = TRUE, c(from = TRUE, to = FALSE),
      fdef = coerceFun, mlist = coerceMethods)
8: as(obj, "integer")
7: isIdCurrent(con)
6: postgresqlQuickSQL(conn, statement, ...)
5: dbGetQuery(con, paste("SELECT tbl  FROM Meta ", where, ";"))
4: dbGetQuery(con, paste("SELECT tbl  FROM Meta ", where, ";"))
3: TSdbi:::TSdeleteSQL(serIDs = serIDs, con = con, ...)
2: TSdelete("vec", con)
1: TSdelete("vec", con)

 >  str(con)

Formal class 'TSPostgreSQLConnection' [package "TSPostgreSQL"] with 4 slots
 ..@ Id     : int [1:2] 21795 1
 ..@ dbname : chr "test"
 ..@ vintage: logi FALSE
 ..@ panel  : logi FALSE
====================================================================================

La version fran?aise suit le texte anglais.

------------------------------------------------------------------------------------

This email may contain privileged and/or confidential in...{{dropped:26}}