CODEWITHSUNDEEP
rr-packageroxygen2r-s3
Nikos Bosse
Nikos Bosse

Reputation: 194

Creating internal S3 methods in package development

I want to use S3 dispatch for an internal function. However, when I create something like

myfun <- function(x) {
  UseMethod("myfun")
}

myfun.someclass <- function(x) {
  print(x)
}

roxygen complains: "S3 method myfun.someclass needs @export or @exportS3method tag."

I figured out that when I rename my function to .myfun(), all is fine.

Is that the rule? You can't have internal S3 methods unless you prepend the function name with a .? I couldn't find any documentation related to that, so I'm a bit confused: Are internal S3 methods generally discouraged in packages and I just found a hack, or is that a fine thing to do?

Upvotes: 2

Views: 82

Answers (1)

Nikos Bosse
Nikos Bosse

Reputation: 194

For S3 methods, @export doesn't actually export the method, but instead registers it. The right way to handle this is to register the S3 methods by adding the @export tag, but not then simply not export the generic function.

Roxygen complains when you don't register an S3 method and from R 3.5 onwards all S3 methods should be registered.

Upvotes: 3

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