On 30/06/2021 5:22 a.m., Taras Zakharko wrote:
Dear all,
I have a generic function and a bunch of methods defined in a separate
environment. Here is a reduced example:
env <- local({
# define the generic function and the method
myfun <- function(x) UseMethod("myfun")
myfun.myclass <- function(x) print("called myfun.myclass”)
# register the method
.S3method("myfun", "myclass", myfun.myclass)
environment()
})
Since the method has been registered, I hoped that invocation like this would
work:
env$myfun(structure(0, class = "myclass”))
However, this results in a “no applicable method" error.
It is my understanding that registerS3method (called by .S3method) will install
the method string in the .__S3MethodsTable__. table of the environment where
the generic function is defined, and this table is subsequently used by
usemethod() inside R, so I am puzzled that the dispatch does not work. I
checked and the .__S3MethodsTable__. of env is indeed setup correctly. I also
tried manually adding the method string to the global .__S3MethodsTable__.
inside .BaseNamespaceEnv to no effect.
In fact, the only way to make it work is to define either myfun or
myfun.myclas in the global environment, which is something I would like to
avoid.
Thank you in advance for any pointers!
registerS3method has an additional parameter "envir" which I believe
would end up set to env in your code. So this works:
> eval(expression(myfun(structure(0, class = "myclass"))), envir = env)
[1] "called myfun.myclass"
You could probably also call registerS3method with envir specified
appropriately and get your original expression to work.
Duncan Murdoch
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