[R-pkg-devel] Working with connections

[Glenn Schultz]

Hi Joshua, Thank-you.  
I did not realize that the call to return closed the connection
-Glenn
> On Aug 9, 2015, at 9:04 AM, Joshua Ulrich <josh.m.ulrich at gmail.com> wrote:
> 
> On Sun, Aug 9, 2015 at 8:59 AM, Glenn Schultz <glennmschultz at me.com> wrote:
>> 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?
>> 
> 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).
> 
>> -Glenn
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> 
> 
> 
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