Dear Developers,
I wonder what are the parent.frame rules for methods. For ordinary functions one
can call parent.frame() and be sure that it is the environment of a calling
function. With S4 aparently it is not the case.
Here is what I have discovered by trial and error so far:
> setClass("A", contains="vector")
[1] "A"
> setGeneric("foo", def=function(a, ...){standardGeneric("foo")})
[1] "foo"
>
> setMethod("foo", signature("A"),
+ def=function(a, ...){
+ cat("--pf1--\n")
+ ls(parent.frame(1))
+ ## cat("--pf2--")
+ ## ls(parent.frame(2))
+ })
[1] "foo"
>
> tf <- function(){
+ b <- 4
+ foo(new("A")) #ok
+ }
>
> tf() #ok
--pf1--
[1] "b"
The above works like predicted.
Now, a small change. The "b" argument which is not in the signature, but has a
role of an additional parameter to the function:
> setMethod("foo", signature("A"),
+ def=function(a, b, ...){
+ cat("--pf1--\n")
+ print(ls(parent.frame(1)))
+ cat("--pf2--\n")
+ print(ls(parent.frame(2)))
+ })
[1] "foo"
>
> tf() #oups
--pf1--
[1] "a"
--pf2--
[1] "b"
>
So, can I be sure that for such functions parent.frame(2) will always work?
What are the additional rules?
Many thanks,
Vitaly.
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