[Rd] Options that are local to the package that sets them

[Gábor Csárdi]

On Fri, Oct 31, 2014 at 8:16 PM, William Dunlap <wdunlap at tibco.com> wrote:
> You can put the following 3 objects, an environment and 2 functions
> that access it, in any package that need some package-specific
> storage (say your pkgB1 and pkgB2).
>    .pkgLocalStorage <- new.env(parent = emptyenv())
>    assignInPkgLocalStorage <- function(name, object) {
>        .pkgLocalStorage[[name]] <- object
>    }
>    getFromPkgLocalStorage <- function(name, object) {
>        .pkgLocalStorage[[name]]
>    }
> Leave the environment private and export the functions.  Then a user can
> use them as
>    pkgB1::assignInPkgLocalStorage("myPallete", makeAPallete(1,2,3))
>    pkgB2::assignInPkgLocalStorage("myPallete", makeAPallete(5,6,7))
>    pkgB1::getFromPkgLocalStorage("myPallete") # get the 1,2,3 pallete

I am trying to avoid requiring pkgBn to do this kind of magic. I just
want it to call function(s) from pkgA. But maybe something like this
would work. In pkgBn:

my_palettes <- pkgA::palette_factory()

and my_palettes is a function or an environment that has the API
functions to modify my_palettes itself (via closure if it is a
function), e.g.

my_palettes$add_palette(...)
my_palettes$get_palette(...)

or if it is a function, then

my_palettes(add(...), ...)
my_palettes(get(...), ...)

etc.

This would work, right? I'll try it in a minute.

Gabor


> If only one of pkgB1 and pkgB2 is loaded you can leave off the pkgBn::.
>
> A package writer can always leave off the pkgBn:: as well.
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
>
> On Fri, Oct 31, 2014 at 4:34 PM, Gábor Csárdi <csardi.gabor at gmail.com> wrote:
>> Dear All,
>>
>> I am trying to do the following, and could use some hints.
>>
>> Suppose I have a package called pkgA. pkgA exposes an API that
>> includes setting some options, e.g. pkgA works with color palettes,
>> and the user of the package can define new palettes. pkgA provides an
>> API to manipulate these palettes, including defining them.
>>
>> pkgA is intended to be used in other packages, e.g. in pkgB1 and
>> pkgB2. Now suppose pkgB1 and pkgB2 both set new palettes using pkgA.
>> They might set palettes with the same name, of course, they do not
>> know about each other.
>>
>> My question is, is there a straightforward way to implement pkgA's
>> API, such that pkgB1 and pkgB2 do not interfere? In other words, if
>> pkgB1 and pkgB2 both define a palette 'foo', but they define it
>> differently, each should see her own version of it.
>>
>> I guess this requires that I put something (a function?) in both
>> pkgB1's and pkgB2's package namespace. As I see it, this can only
>> happen when pkgA's API is called from pkgB1 (and pkgB2).
>>
>> So at this time I could just walk up the call tree and put the palette
>> definition in the first environment that is not pkgA's. This looks
>> somewhat messy, and I am probably missing some caveats.
>>
>> Is there a better way? I have a feeling that this is already supported
>> somehow, I just can't find out how.
>>
>> Thanks, Best Regards,
>> Gabor
>>
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