[ftype] Question regarding the s3 method type

[dhuebner]

I have a question regarding the usage of pryr functions in own code.
Following is a function I've created:
f <- function(var) {pryr::ftype(var)}

Calling "ftype" directly for 't.data.frame' results in an expected output:

pryr::ftype(t.data.frame)
[1] "s3" "method"`

Calling the same 't.data.frame' from my function prints a wrong result:

f(t.data.frame)
[1] "function"

Is there some trick for "S3 method" recognition ?

[marami52]

@dhuebner you always ask hard and good questions! :) I couldn't figure it out. I sent an email to Hadely (author of pryr) and will keep you posted.

[alexey0308]

Hi Dennis @dhuebner,

ftype uses parent.frame() in order to derive the type (in this case, the environment of
the function f call).

You may use this workaround in order to go one level back
(or, for example, to the global environment, if env=.GlobalEnv):

> f <- function(var, env=parent.frame()) {
+     eval(substitute(pryr::ftype(var)), envir = env)
+ }
> 
> f(t.data.frame)
[1] "s3"     "method"

Hope this helps.

Regards,
Alex