On Fri, Jan 23, 2009 at 1:25 AM, Biczok Rudolf
<r.bic...@dkfz-heidelberg.de> wrote:
> Hi all,
> I'm working with the S4-Class system and I have a little problem with
> Implementing iteration functionality in my S4 class but it don't work:
>> setClass("foo",representation(bar="list"))
>> x <- new("foo",bar=list(1,2,3))
>>for(e in x) cat(e)
> invalid type/length (S4/1) in vector allocation
I'm not sure why you would expect a for loop to work there. Wouldn't
a function in the "apply" family be more natural? At least in my code
it is much more common to use lapply to loop over the elements of a
list than it is to use 'for'.
I once suggested to John Chambers that it would be a good idea to have
a way of applying a function to the slots of an S4 object and he
persuaded me otherwise. However, you can generate something like that
with
lapply(slotNames(x), function(nm) cat(slot(x, nm)))
or create a list out of the S4 object
S4toL <- function(x) {nms <- slotNames(x); names(nms) <- nms;
lapply(nms, slot, object = x)}
then use lapply on the result of S4toL
>
>
>
>
>
> But when I extend from a primitive vector it works:
>
>
>
>> setClass("foo",contains="list")
>
>
>
>> x <- new("foo",.Data=list(1,2,3))
>
>
>
>>for(e in x) cat(e)
>
> 123
>
>
>
> This is ok, but is there any other way to do this (for e.g. with a
> generic function)?
>
>
>
> Thanks,
>
> Rudolf
>
>
> [[alternative HTML version deleted]]
>
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