On 4/2/2009 9:41 AM, Whit Armstrong wrote:
Thanks to everyone for the suggestions.
The package local environment (per Roger Peng) works well.
.localstuff <- new.env()
.localstuff$bbg.db.conn <- dbConnect(...)
However, there is one thing that I'm confused about.
Why must the .localstuff variable be an environment?
If a package doesn't have a namespace, then its functions have their
environment set to the global environment, so they can stomp on user
things by accident. I'd say a better solution to this problem is that
every package should have a namespace, then there isn't the same risk of
messing with a user's variables.
I've tried the following, but the variable conn stays null during the
whole R session. Despite the database connection succeeding (I can
see the constructor printing to the console):
conn <- NULL
.onAttach <- function(libname, pkgname) {
conn <- dbConnect(dbDriver("PostgreSQL"), user="...")
}
That creates a new local variable called conn. Use
conn <<- dbConnect ...
to modify the package one. (Assuming you have a namespace; if not, that
will have different effects depending on whether or not the user has a
variable named conn. Yecch.)
Duncan Murdoch
.onUnload <- function(libpath) {
dbDisconnect(conn)
}
output from R session:
[warmstr...@linuxsvr R.packages]$ R
library(KLS)
Loading required package: fts
Loading required package: RCommodity
Loading required package: unifiedDBI
Loading required package: RFincad
Loading required package: RLIM
Loading required package: RBoostDateTime
PostgresConnection::PostgresConnection()
KLS:::conn
NULL
x <- get.bbg("EURUSD Curncy")
Error in get.bbg("EURUSD Curncy") : Database connection not initialized
q()
PostgresConnection::~PostgresConnection()
[warmstr...@linuxsvr R.packages]$
Thanks,
Whit
On Tue, Mar 31, 2009 at 3:51 PM, Philippe Grosjean
<phgrosj...@sciviews.org> wrote:
The best way is to have those variable hidden in the package's workspace, as
explained by Roger Peng.
However, if you like to use a mechanism managing an environment specifically
dedicated to temporary variables very easily, look at assignTemp() and
getTemp() from svMisc package. The advantage is an easier sharing of such
variables between different packages (plus the bonus of easy management of
default values, overwriting or not of current content if the variable
already exists, ...). The temporary environment (TempEnv) is always located
in the forelast position just before 'base'.
In any cases, avoid using .GlobalEnv and the ugly <<- for that purpose.
Best,
Philippe Grosjean
Roger Peng wrote:
I usually use environments for this. So, in one of the R files for the
package, just do
.localstuff <- new.env()
Then, in functions you can do things like
.localstuff$bbg.db.conn <- dbConnect(...)
-roger
On Tue, Mar 31, 2009 at 11:45 AM, Whit Armstrong
<armstrong.w...@gmail.com> wrote:
for the moment, I'm using:
.onAttach <- function(libname, pkgname) {
.bbg.db.conn <<- dbConnect(dbDriver("PostgreSQL"), user="blah","blah")
}
.onUnload <- function(libpath) {
dbDisconnect(.bbg.db.conn)
}
which results in a hidden global variable in the global environment.
I would prefer to make the assignment only in the package namespace.
I've looked at assignInNamespace, but I can't seem to make it work.
Is there a preferred method for doing this?
When I try adding an assignment directly in the source file, I get the
"cannot change value of locked binding" error.
What am I missing?
Thanks,
Whit
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