Updating embedded data, for example sysdata.rda

Question

My latest submission to CRAN got bounced back because I have assignments to the global environment which is now frowned upon.

I have an embedded data set (sysdata.rda) that contains configuration parameters based upon state (as in United States) the user resides. I have wanted this embedded data set to be updatable when a new user uses the program. I previously updated this data in the initial function the user uses and made it accessible to the user via global assignment.

I am struggling to figure out how to update this embedded data and make it the default data that the user uses for the remainder of their session.

Previously I housed the data in /data and recently switched it to /R/sysdata.rda as it seemed more suited for that locale. Now I'm not so sure.

Any help greatly appreciated

Answer 1

The key is to do the assignment in an environment other than the global environment. There are two basic techniques, using local() and <<- or explicitly creating a new environment:

Working with an explicit environment is straightforward: create the environment and then assign into it like a list:

my_opts <- new.env(parent = emptyenv())
set_state <- function(value) my_opts$state <- value
get_state <- function() my_opts$state

Using local() is a little more complex, and requires some tricks with <<-

set_state <- NULL
get_state <- NULL

local({
  state <- NULL
  get_state <<- function() state
  set_state <<- function(value) state <<- value
})

For more info on how <<- works see https://github.com/hadley/devtools/wiki/environments, in the "Assignment: binding names to values" section.