How do we set constant variables while building R packages?

Question

We are building a package in R for our service (a robo-advisor here in Brazil) and we send requests all the time to our external API inside our functions.

As it is the first time we build a package we have some questions. :(

When we will use our package to run some scripts we will need some information as api_path, login, password.

How do we place this information inside our package?

Here is a real example:

get_asset_daily <- function(asset_id) {
    api_path <- "https://api.verios.com.br"

    url <- paste0(api_path, "/assets/", asset_id, "/dailies?asc=d")
    data <- fromJSON(url)
    data
}

Sometimes we use a staging version of the API and we have to constantly switch paths. How we should call it inside our function?

Should we set a global environment variable, a package environment variable, just define api_path in our scripts or a package config file?

How do we do that?

Thanks for your help in advance.

Ana

Answer 1

One approach would be to use R's options interface. Create a file zzz.r in the R directory (this is the customary name for this file) with the following:

.onLoad <- function(libname, pkgname) {
    options(api_path='...', username='name', password='pwd')

}

This will set these options when the package is loaded into memory.