Return a list of fields of a Reference Class

Question

What is the proper way to define a function which returns a arbitrary number of fields.

  A.getFields<-function(values){
  vars<-getRefClass()$fields()
  idx<-names(vars) %in% values
  if(length(fields)<1) 
    return(vars)
  return(vars[idx])
}
A.setFields<-function(...){
  dots <- list(...)
  fieldNames <- names(dots)
  for(i in seq_along(dots))
    assign(fieldNames[[i]], dots[[i]], attr(.self, ".xData"))
}
A<-setRefClass(Class = "A",
               fields = c(var1 = "list",
                          var2="character"),
               methods = list(getFields=A.getFields
                              ,setFields=A.setFields
                              ,initialize=function(...,var1=list(), var2=character()) {
                                obj<-list(...)[[1]]
                                if(is(obj,"list"))
                                  do.call(.self$setFields,obj)
                                else{
                                  .self$var1<-as.list(var1)
                                  .self$var2<-as.character(var2)
                                }
                                .self
                              })
)

a<-A(var1=list(1:3),var2="A")
a$getFields(c("var2"))
a$getFields(c("var2","var1"))

score 2 · Accepted Answer · answered Sep 10 '13 at 10:46

2

The reference class definition can be queried for defined fields, e.g.,

getRefClass("A")$fields()
a = A()
a$getRefClass()$fields()

so maybe

A = setRefClass("A", fields=c(var1="list", var2="character"),
    methods=list(getFields=function(values) {
        flds = names(getRefClass()$fields())
        if (!missing(values))
            flds = flds[flds %in% values]
        result = setNames(vector("list", length(flds)), flds)
        for (fld in flds)
            result[[fld]] = .self[[fld]]
        result
    }))

with

> A(var2=letters[1:5])$getFields("var2")
$var2
[1] "a" "b" "c" "d" "e"

answered Sep 10 '13 at 10:46

Martin Morgan

45,935
7
84
112

Many thx, is there a general differnt to the following function for getFields? `A.getFields<-function(values){ vars<-getRefClass()$fields() idx<-names(vars) %in% values if(length(fields)<1) return(vars) return(vars[idx]) }` – Klaus Sep 10 '13 at 11:19
@Klaus The code does not work as written, but seems to return the types of the fields rather than their values – Martin Morgan Sep 10 '13 at 14:18
You are right `A.getFields<-function(values){ vars<-mget(names(.refClassDef@fieldClasses), envir = attr(.self, ".xData")) if(missing(values)) , sry I read this post to late. return(vars) return(vars[names(vars) %in% values]) }` is what I suggested this is the function is from [here](http://stackoverflow.com/questions/18639140/how-to-debug-methods-from-reference-classes?noredirect=1#comment27442400_18639140) – Klaus Sep 10 '13 at 15:58

Return a list of fields of a Reference Class

1 Answers1

Linked