Construct a Representation or a Prototype for a Class Definition
These are old utility functions to construct, respectively
a list designed to represent the slots and superclasses and
a list of prototype specifications. The
function is no longer useful, since the arguments
setClass are now recommended.
prototype() function may still be used for the
corresponding argument, but a
simple list of the same arguments works as well.
The call to representation takes arguments that are single character
strings. Unnamed arguments are classes that a newly defined class
extends; named arguments name the explicit slots in the new class,
and specify what class each slot should have.
In the call to
prototype, if an unnamed argument is supplied, it unconditionally forms the basis for the prototype object. Remaining arguments are taken to correspond to slots of this object. It is an error to supply more than one unnamed argument.
representation function applies tests for the validity of
the arguments. Each must specify the name of a class.
The classes named don't have to exist when
called, but if they do, then the function will check for any duplicate
slot names introduced by each of the inherited classes.
The arguments to
prototype are usually named initial values
for slots, plus an optional first argument that gives the object
itself. The unnamed argument is typically useful if there is a data
part to the definition (see the examples below).
The value of
representationis just the list of arguments, after these have been checked for validity.The value of
prototypeis the object to be used as the prototype. Slots will have been set consistently with the arguments, but the construction does not use the class definition to test validity of the contents (it hardly can, since the prototype object is usually supplied to create the definition).
Chambers, John M. (2008) Software for Data Analysis: Programming with R Springer. (For the R version.)
Chambers, John M. (1998) Programming with Data Springer (For the original S4 version.)
## representation for a new class with a directly define slot "smooth" ## which should be a "numeric" object, and extending class "track" representation("track", smooth ="numeric") setClass("Character",representation("character")) setClass("TypedCharacter",representation("Character",type="character"), prototype(character(0),type="plain")) ttt <- new("TypedCharacter", "foo", type = "character") setClass("num1", representation(comment = "character"), contains = "numeric", prototype = prototype(pi, comment = "Start with pi"))