(Can we please follow the terminology in the ?ReferenceClasses
documentation. Creativity is fine but here we need communication)
This has come up (once) before off-list. It could be made part of
reference classes via a general rewriting that would improve efficiency
as well. Not imminent, but it would be good to know of other
applications, including why they are useful.
Meanwhile, it could be implemented for a subclass of reference classes,
by adding a special field that lists the private (or public, if you
like) fields, and then implementing S4 methods for "$" and "$<-" that
check there for disallowed/allowed names. As presumably one wants, this
leaves methods in the class free to use the private fields.
John
On 2/21/12 3:07 AM, Claus Jonathan Fritzemeier wrote:
Hi list,
is there a way to define some kind of private Variable?
I would like to prevent the user from manipulating fields on his own,
in order to not destroy data structures.
The problem is, that as soon as the variable exists in the environment
it is accessible via t$secret_value.
test <- setRefClass("test", fields=list(
secret = function(value){
cat("the function was called\n")
if(missing(value)){
if(exists("secret_value", envir=.self@.xData)){
return(get("secret_value", envir=.self@.xData, inherits = F))
}
else{
return(NULL)
}
}
assign("secret_value", value=value, , envir=.self@.xData)
}
) )
> t <- test$new()
> t$secret
the function was called
NULL
> t$secret_value
Error in envRefInferField(x, what, getClass(class(x)), selfEnv) :
"secret_value" is not a valid field or method name for reference class
“test”
> t$secret <- "Blub"
the function was called
> t$secret_value
[1] "Blub"
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