CODEWITHSUNDEEP
rdevtoolsr-package
dark-walrus
dark-walrus

Reputation: 111

How to set global package variables so they can be accessed by examples in R CMD check?

I am working on an R package right now that includes example images that can be used. I want to set it up so the paths to those images are stored in a global variable that can be accessed either by loading the package or by using something like myPackage::myVar.

Currently, I have the images in the inst/media folder and set variables containing their paths in the .onLoad function in my zzz.R file; the function looks like this:

.onLoad = function(libname, pkgname) {
    dog = system.file("media", "dog.png", package="myPackage")
    assign("dog", dog, envir=parent.env(environment()))
}

When I load my package with devtools::load_all(), I can access the variable with just dog. However, when I build with devtools::build() and install manually, I can only access the variable with myPackage:::dog.

Further, I have an example in my man pages generated with roxygen that uses the following code:

ret = parsePath(dog)

When I run devtools::check() it returns an error with this warning saying Error : object dog not found.

Is there any way that I can add this global variable in a way that allows me to access them by loading the package and typing the name, and allows the examples to run without error during R CMD check?

Upvotes: 0

Views: 283

Answers (1)

dark-walrus
dark-walrus

Reputation: 111

The issue was that while the dog variable was being assigned to the environment, it was not being exported by the package; the solution is to export the variable as described in this post.

The variable is first assigned to the environment with the .onLoad function:

.onLoad = function(libname, pkgname) {
    dog = system.file("media", "dog.png", package=pkgname)
    assign("dog", dog, envir=parent.env(environment()))
}

Then in a separate file, the variable is exported in quotes like such:

#' @name dog
#' @title The path to an image of a Dog
#' @export
"dog"

I also had to manually add export(dog) to the NAMESPACE file before roxygen did it automatically for me. This allows the variable to be accessed by myPackage::dog. Without exporting the variable in quotes, the variable could only be accessed with myPackage:::dog and would not be seen by other functions using just dog. This also passes devtools::check.

Upvotes: 0

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