R devel - Apr 2011 - Reference Classes: Accessing methods via [[...]], bug?

I've been trying to use methods for reference classes via the notation
"[[...]]" (X[["doSomething"]] rather than X$doSomething),
but it failed to work. However, I did find that if you use the usual
"$" notation first, "[[...]]" can be used afterwards. The
following simple example illustrates the point:
> setRefClass("Number", +   fields = list(+     value =
"numeric"+   ),+   methods = list(+     addOne = function() {+      
value <<- value + 1+     }+   )+ )> X <- new("Number",
value = 1)> X[["value"]][1] 1
> X[["addOne"]]()Error: attempt to apply non-function>
class(X[["addOne"]]) # NULL[1] "NULL"
> class(X$addOne)[1] "refMethodDef"attr(,"package")[1]
"methods"
> X[["addOne"]]()> X[["value"]][1] 2>
class(X[["addOne"]])[1]
"refMethodDef"attr(,"package")[1] "methods"
Is this a bug?
Chad Goymer
 		 	   		  
	[[alternative HTML version deleted]]

If this message is garbled for anyone else, the original question on
stackoverflow is here:
http://stackoverflow.com/questions/5841339/using-notation-for-reference-class-methods

Hadley

On Sat, Apr 30, 2011 at 11:35 AM, Chad Goymer <chad.goymer at
hotmail.co.uk> wrote:
>
> I've been trying to use methods for reference classes via the notation
"[[...]]" (X[["doSomething"]] rather than X$doSomething),
but it failed to work. However, I did find that if you use the usual
"$" notation first, "[[...]]" can be used afterwards. The
following simple example illustrates the point:
>> setRefClass("Number", + ? fields = list(+ ? ? value =
"numeric"+ ? ),+ ? methods = list(+ ? ? addOne = function() {+ ? ? ?
value <<- value + 1+ ? ? }+ ? )+ )> X <- new("Number",
value = 1)> X[["value"]][1] 1
>> X[["addOne"]]()Error: attempt to apply non-function>
class(X[["addOne"]]) # NULL[1] "NULL"
>> class(X$addOne)[1]
"refMethodDef"attr(,"package")[1] "methods"
>> X[["addOne"]]()> X[["value"]][1] 2>
class(X[["addOne"]])[1]
"refMethodDef"attr(,"package")[1] "methods"
> Is this a bug?
> Chad Goymer
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>


-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/