[R-pkg-devel] Is there a better way ...?
On Thu, Oct 21, 2021 at 9:59 AM Rolf Turner <r.turner at auckland.ac.nz> wrote:
I have a plot method (say plot.foo()) that I want to be able to call so that if argument "add" is set equal to TRUE, then further structure will be added to the same plot. This is to be used *only* in the context in which the plot being added to was created using plot.foo(). [Please don't ask me why I don't do everything in a single call to plot.foo(). There *are* reasons.] In order to make sure that the "further structure" has the appropriate form, the call to plot.foo(...,add=TRUE,...) needs to access information about what was done in the previous call to plot.foo(). Initially I tried to effect this by creating, in a call of the form plot.foo(...,add=FALSE,...), an object, say ".fooInfo", in the global environment, and then having the call plot.foo(...,add=TRUE,...) access the necessary information from ".fooInfo".
Why not have a private (unexported) environment in your own package for the same purpose? (That's the strategy used by lattice.) E.g., in your zzz.R .FooEnv <- new.env() and then have your plot.foo write into / read from that. Long term, it may be better to write accessor functions (which can still be unexported if only used by your package code) if you want an implementation-agnostic interface. Best, -Deepayan
It all worked OK, but when I built my package for Windoze, using win-builder, I got a note of the form:
NOTE
Found the following assignment to the global environment:
File 'pckgename/R/plot.foo.R':
assign(".fooInfo", fooInfo, pos = 1)
I thought uh-oh; CRAN will kick up a stink if/when I submit my package. I think I've figured out a work-around using tempfile(). There are difficulties in that tempfile() creates unique names by tacking on an alpha-numeric string such as "38348397e595c" to the file name that I specify, so the call to plot.foo(...,add=TRUE,...) cannot know the *exact* file name. I think I can get around that by grepping on "fooInfo" in list.files(tempdir()). I also need to make sure that I unlink() any old instances of files in tempdir() with the string "fooInfo" in their names before creating a new instance. Elsewise ambiguities will ensue. As I say --- I think this can all be made to work. But .... Am I missing some "obvious" strategy? I.e. is there a better/simpler/less convoluted way of handling this problem? Grateful for any pearls of wisdom. cheers, Rolf Turner -- Honorary Research Fellow Department of Statistics University of Auckland Phone: +64-9-373-7599 ext. 88276
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