setClass("Layer", contains = "VIRTUAL")
setClass("LayerList", contains = "list")
setClassUnion("LayerListORNULL", c("LayerList","NULL"))
## validation
setValidity("LayerList", function(object){
res <- unlist(lapply(object, is, "Layer"))
if(all(res))
TRUE
else
paste("Entry ", which(!res), " is not Layer object(returned by qlayer)")
})
## LayerList API
LayerList <- function(...){
lst <- list(...)
if(length(lst) == 1 && is.list(lst[[1]]))
lst <- lst[[1]]
## validation
isLayer <- unlist(lapply(lst, is, "Layer"))
if(!all(isLayer))
stop(paste("Entry ", which(!isLayer), " is not Layer object(returned by qlayer)"))
new("LayerList", lst)
}
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