gistfile1.r

tc <- setRefClass(Class="testClass",
        fields = list(f1="numeric", f2="numeric"),
        representation=representation(x="character")
        )

t1 <- tc$new(f1=4, f2=5, x="a")
t2 <- t1
t2@x <- "b"
t1
t2
(t3 <- t1$copy())