在R5参考类中定义类方法和类变量

> # define R5 class XX
> # member variable: ma
> # member method: mfa
> XX <- setRefClass(\"XX\",
+   fields = list(ma = \"character\"),
+   methods = list(
+     mfa = function() return(paste(ma, \"*\"))
+     ))
> 
> XX
Generator object for class \"XX\":

Class fields:

Name:         ma
Class: character

 Class Methods:  
    \"callSuper\", \"copy\", \"export\", \"field\", \"getClass\", \"getRefClass\", \"import\", \"initFields\", 
\"mfa\"


 Reference Superclasses:  
    \"envRefClass\"

> # create an instance of XX
> x <- XX$new(ma=\"ma\")
> 
> # call member method refering to the member variable.
> x$mfa()
[1] \"ma *\"
> 
> # here, I define *class* variable
> XX$cc <- \"cc\"

> # contents of XX
> ls(XX)
[1] \"cc\"        \"className\" \"def\"       \"methods\"   \"new\"      

> # here, I define member method referring to the class var.
> XX$methods(mfc = function() {
+   return(XX$cc)
+ })

> # it does work.
> x$mfc()
[1] \"cc\"

XX$cc <- \"cc\"