Rclass

RClass, short for reference class, refers to the reference class system in the R programming language. It provides mutable objects and true reference semantics, in contrast to the copy-on-modify behavior common with S3 and S4 objects. The system is implemented in the methods package through setRefClass and is often called RC or a reference class framework.

A class defined with RClass specifies fields (data members) and methods (functions). An optional initialize method can set up initial values when an object is created. Objects created with new are reference objects, meaning multiple references can point to the same underlying object and changes via one reference are visible to all others. Inheritance is supported through the contains argument, allowing RC classes to extend other RC classes and reuse behavior.

Usage typically involves defining a class with fields and methods, creating an instance with new, and interacting through the $ operator to access or modify fields and to call methods. This enables in-place modification of object state, which can simplify certain data-processing patterns or simulations where shared, mutable state is natural.

Compared with S3 and S4, RC emphasizes mutable state and explicit reference semantics, but can be more verbose and harder to debug due to its mutable nature. It is less ubiquitous in modern R code than S3/S4, and some developers prefer alternatives. A contemporary option for reference-style OO in R is the R6 package, which provides a cleaner, more widely used approach to reference classes with a similar philosophy but different syntax.

See also: S3, S4, RC, R6, setRefClass.