Class Union

> setClass("A", representation = representation(name = "character"),
+     prototype = prototype(name = "vinay"))
[1] "A"
> getClass("A")
Class "A"

Slots:

Name:       name
Class: character
> setMethod("initialize", "A", function(.Object, ..., who = "vinay") {
+     .Object@name <- who
+     .Object
+ })
[1] "initialize"
> x <- new("A", )
> print(x)
An object of class "A"
Slot "name":
[1] "vinay"
> setGeneric("getPerson", function(object) standardGeneric("getPerson"))
[1] "getPerson"
> showMethods("getPerson")
Function: getPerson (package .GlobalEnv)
<No methods>
> setMethod("getPerson", "A", function(object) {
+     "vinay"
+ })
[1] "getPerson"
> x <- new("A", )
> print(x)
An object of class "A"
Slot "name":
[1] "vinay"
> getPerson(x)
[1] "vinay"
> setClass("Sub1", representation = representation(interest = "character"),
+     prototype = prototype(interest = "statistics"))
[1] "Sub1"
> getClass("Sub1")
Class "Sub1"

Slots:

Name:   interest
Class: character
> setMethod("initialize", "Sub1", function(.Object, ..., what = "statistics") {
+     .Object <- callNextMethod()
+     .Object@interest <- what
+     .Object
+ })
[1] "initialize"
> x <- new("Sub1")
> print(x)
An object of class "Sub1"
Slot "interest":
[1] "statistics"
> setClass("Sub2", representation = representation(interest = "character"),
+     prototype = prototype(interest = "R"))
[1] "Sub2"
> getClass("Sub2")
Class "Sub2"

Slots:

Name:   interest
Class: character
> setMethod("initialize", "Sub2", function(.Object, ..., what = "R") {
+     .Object <- callNextMethod()
+     .Object@interest <- what
+     .Object
+ })
[1] "initialize"
> x <- new("Sub2")
> print(x)
An object of class "Sub2"
Slot "interest":
[1] "R"

> setClassUnion("A", c("Sub1", "Sub2"))
[1] "A"
> x <- new("Sub2")
> x
An object of class "Sub2"
Slot "interest":
[1] "R"
> getPerson(x)
[1] "vinay"