[R] S4 non-virtual class with no slots?
martin.morgan at roswellpark.org
Fri Apr 22 23:36:08 CEST 2016
On 04/22/2016 04:38 PM, Boylan, Ross wrote:
> It seems that if an S4 class has no slots it can't be instantiated because it is assumed to be virtual. Is there a way around this other than adding a do-nothing slot? A singleton would be OK, though is not essential.
> EmptyFitResult <- setClass("EmptyFitResult", representation=representation())
> # also tried it without the second argument. same result.
> > e <- EmptyFitResult()
> Error in new("EmptyFitResult", ...) :
> trying to generate an object from a virtual class ("EmptyFitResult")
> This in R 3.1.1.
> I fit simulated data; in some simulations none survive to the second stage of fitting. So I just need a way to record that this happened, in a way that integrates with my other non-null results.
A not too artificial solution is to create a base class, with derived
classes corresponding to stateless or stateful conditions
Base = setClass("Base"); A = setClass("A", contains="Base"); A()
> Ross Boylan
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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