R中的延迟包依赖

Question

I'd like to write a R package. A small part of its functionality would be to save data into xlsx file. But this functionality would require a big and heavy dependency: library(xlsx) . So I'd like to make this dependency somehow optional and lazy-loaded.

What is the Best Practice for it?

I guess I could simply library(xlsx) in the code of the function that need it, and handle possible failures of this command.

Answer 1

I believe the most robust way to do this is the add the following line to the NAMESPACE of your package:

importFrom(xlsx, the_function_you_need)

along with

Depends: xlsx

in the DESCRIPTION file. As far as I understand, this will give your package access to the function you want without loading the entire library. There is some discussion of importFrom here: What is the benefit of import in a namespace in R?