[Rd] S4 fails to initialize linear hierarchies with intermediate VIRTUAL classes
mtmorgan at fhcrc.org
Thu Oct 18 15:31:44 CEST 2012
Initialization of this simple hierarchy
A = setClass("A", representation(x="numeric"))
setClass("B", contains=c("VIRTUAL", "A"))
C = setClass("C", contains="B")
fails (neat that setClass returns generators; I hadn't realized that before!)
Error: evaluation nested too deeply: infinite recursion / options(expressions=)?
because in the default coerce<-,C,A-method
> selectMethod("coerce<-", c("C", "A"))
function (from, to = "A", value)
.value <- as(from, "B", TRUE)
as(.value, "A") <- value
as(from, "B", TRUE) correctly returns an instance of C.
Also VIRTUAL isn't mentioned on ?Classes or ?setClass and isn't documented on
class?VIRTUAL, making me wonder whether virtual classes are actually meant to be
supported as part of S4 (they are used regularly in Bioconductor packages)?
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