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##
## $Id: dbObjectId.R 80 2002-09-10 11:50:46Z dj $
##
## Copyright (C) 1999-2002 The Omega Project for Statistical Computing.
##
## This library is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public
## License as published by the Free Software Foundation; either
## version 2 of the License, or (at your option) any later version.
##
## This library is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public
## License along with this library; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##
## Class: dbObjectId
##
## This mixin helper class is NOT part of the database interface definition,
## but it is extended by the Oracle, MySQL, and SQLite implementations to
## MySQLObject and OracleObject to allow us to conviniently (and portably)
## implement all database foreign objects methods (i.e., methods for show(),
## print() format() the dbManger, dbConnection, dbResultSet, etc.)
## A dbObjectId is an identifier into an actual remote database objects.
## This class and its derived classes <driver-manager>Object need to
## be VIRTUAL to avoid coercion (green book, p.293) during method dispatching.
##
## TODO: Convert the Id slot to be an external object (as per Luke Tierney's
## implementation), even at the expense of S-plus compatibility?
setClass("dbObjectId", representation(Id = "integer", "VIRTUAL"))
## coercion methods
setAs("dbObjectId", "integer",
def = function(from) as(slot(from,"Id"), "integer")
)
setAs("dbObjectId", "numeric",
def = function(from) as(slot(from, "Id"), "integer")
)
setAs("dbObjectId", "character",
def = function(from) as(slot(from, "Id"), "character")
)
## formating, showing, printing,...
setMethod("format", "dbObjectId",
def = function(x, ...) {
paste("(", paste(as(x, "integer"), collapse=","), ")", sep="")
},
valueClass = "character"
)
setMethod("show", "dbObjectId", def = function(object) print(object))
setMethod("print", "dbObjectId",
def = function(x, ...){
expired <- if(isIdCurrent(x)) "" else "Expired "
str <- paste("<", expired, class(x), ":", format(x), ">", sep="")
cat(str, "\n")
invisible(NULL)
}
)
"isIdCurrent" <-
function(obj)
## verify that obj refers to a currently open/loaded database
{
obj <- as(obj, "integer")
.Call("RS_DBI_validHandle", obj, PACKAGE = .MySQLPkgName)
}
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