[R-pkg-devel] Conditionally register method with generic in other package
We use this technique in a couple of places: https://github.com/tidyverse/dbplyr/blob/6be777d8b23d588f19c98de52f4e58f16c2ef67e/R/zzz.R Basic idea is to call registerS3method() manually, when needed - it's just a little tricky because the suggested package may be loaded either before or after your package. Hadley
On Thu, Dec 7, 2017 at 1:45 AM, Joshua Ulrich <josh.m.ulrich at gmail.com> wrote:
I have a feeling I know the answer to this question, but I'm asking with the hope that I learn something new. Package A defines a S3 generic function, "foo()". Package B defines a S3 class "bar", and a foo.bar() method. This method is not strictly necessary for the package to function, and package A has many dependencies. To avoid excessive dependencies, I would like to only register foo.bar() if package A is installed at the time package B is installed. If package A is installed after package B, then warn the user when package B is loaded and/or attached, so they can re-install A and have foo.bar() registered correctly. I could figure out a way to do this manually, but doubt it would be CRAN-approved. What is the recommended way to handle this situation? I've received one suggestion to split B into 2 packages: one without the method, and one with. Are there other alternatives? Thanks, Josh -- Joshua Ulrich | about.me/joshuaulrich FOSS Trading | www.fosstrading.com R/Finance 2018 | www.rinfinance.com
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