For those looking for an answer to this. No, there is no way to restrict a list in S4 to have elements of certain type. This actually makes sense, since lists in R are designed to contain any type of element, so why lists on S4 should be distinct?
R S4 slots as lists of custom classes
質問
Is it possible to have slots in a S4 class to be lists of another custom type? like
setClass("customClass",
representation(list(anotherCustomClass)
)
解決
他のヒント
Here is a fairly simple implementation of a typed list using S4. Checks that all objects are of the specified type and that all of these objects are validObjects of that type.
instanceof = function(object, type) {
class(object)[[1]] == type
}
typed_list_check = function(object) {
errors = character()
is_correct_object_type = logical()
if (length(object@objects) >= 1) {
for (i in 1:length(object@objects)) {
obj = object@objects[[i]]
is_correct_object_type[[i]] = instanceof(obj, object@type)
}
if (any(!is_correct_object_type)) {
msg = sprintf("At least one object is not of type %s.", object@type)
errors = c(errors, msg)
}
if (all(is_correct_object_type)) {
for (obj in object@objects) {
potential_msg = validObject(obj)
if (is.character(potential_msg)) {
msg = potential_msg
errors = c(errors, msg)
}
}
}
}
if (length(errors) == 0) TRUE else errors
}
setClass(
"TypedList",
representation(
type = "character",
objects = "list"
),
validity = typed_list_check
)
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