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[R-pkg-devel] Working with connections

4 messages · Glenn Schultz, Joshua Ulrich, Hadley Wickham

#
Hi All,?

I use connections to open and close data folders needed by my package. ?After each function closes I get the following warnings (depending on the connection that has been opened).

10: closing unused connection 3 (/Library/Frameworks/R.framework/Versions/3.2/Resources/library/BondLab/BondData/bondlabMBS4.rds)?

Below is the connection function that is related to the above warning:
? #------------------------------------------------------------------------------------
? #' A connection function to BondData calling MBS cusps
? #'?
? #' Opens a connection to the BondData folder to call MBS cusip data?
? #' @param MBS.id A character string the MBS.id or cusip number current MBS.id is supported
? #' @export
? MBS <- function(MBS.id = "character"){
? ? ? ? ? ? ? ? ? MBS.Conn <- gzfile(description = paste(system.file(package = "BondLab"),
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "/BondData/", MBS.id, ".rds", sep = ""), open = "rb") ? ? ? ? ?
? ? ? ? ? ? ? ? ? MBS <- readRDS(MBS.Conn)
? ? ? ? ? ? ? ? ? return(MBS)
? ? ? ? ? ? ? ? ? close.connection(MBS.Conn)
? ? ? ? ? ? ? ? ? }

I have googled this warning and it seems to be triggered when a function terminates and the connection is open. ?But, I think the connection function closes the connection once the object is returned. ?What am I doing wrong?

-Glenn
#
On Sun, Aug 9, 2015 at 8:59 AM, Glenn Schultz <glennmschultz at me.com> wrote:
Your call to return() exits the function, so the close.connection()
call is never evaluated.  Considering using on.exit() to close the
connection, since it will close the connection regardless of how the
function exits (e.g. because of an error).

  
    
#
Hi Joshua, Thank-you.  
I did not realize that the call to return closed the connection
-Glenn
#
Also it's a little strange to put an RDS file _inside_ a gz, since
normally the compression is done internally.

And are you sure you should be exposing this data via a function,
rather than using the regular package data mechanism?

Hadley
On Sun, Aug 9, 2015 at 7:04 AM, Joshua Ulrich <josh.m.ulrich at gmail.com> wrote: