R6 Classes

R6 Classes

R6 is an R package that provides a modern way of using object-oriented programming (OOP) in R. Unlike R's traditional S3 and S4 class systems, R6 classes come with reference semantics, which means you can modify an object in place without creating a copy. Here's a basic tutorial on R6 classes:

1. Installing and Loading R6

Before you can use R6, you need to install and load it:

install.packages("R6") library(R6)

2. Defining an R6 Class

To define an R6 class, use the R6Class() function. A class generally contains public fields (attributes) and methods (functions).

Person <- R6Class("Person", public = list( name = NULL, age = NULL, initialize = function(name = NA, age = NA) { self$name <- name self$age <- age cat("A new person has been initialized!\n") }, set_age = function(value) { self$age <- value }, print_age = function() { cat(self$name, "is", self$age, "years old.\n") } ) )

3. Creating an R6 Object

Once you have defined the class, you can create objects from it:

alice <- Person$new(name = "Alice", age = 30)

4. Accessing Fields and Methods

With R6, you can directly access fields and methods:

# Access field cat("Name:", alice$name, "\n") # Use method alice$print_age() # Modify age alice$set_age(31) alice$print_age()

5. Private Members

R6 allows for private fields and methods which are not directly accessible from outside the object:

BankAccount <- R6Class("BankAccount", private = list( balance = 0 ), public = list( deposit = function(amount) { private$balance <- private$balance + amount cat("Deposited:", amount, "\n") }, withdraw = function(amount) { private$balance <- private$balance - amount cat("Withdrew:", amount, "\n") }, get_balance = function() { return(private$balance) } ) ) account <- BankAccount$new() account$deposit(100) account$withdraw(50) cat("Balance:", account$get_balance(), "\n")

Note: The private balance field cannot be accessed directly from the outside.

6. Inheritance

R6 supports inheritance. One class can inherit fields and methods from another class:

Student <- R6Class("Student", inherit = Person, # Inheriting from the Person class public = list( grade = NA, initialize = function(name, age, grade) { super$initialize(name, age) # Call the initialize method of the parent class self$grade <- grade }, print_grade = function() { cat(self$name, "has a grade of", self$grade, "\n") } ) ) bob <- Student$new(name = "Bob", age = 20, grade = "A") bob$print_age() bob$print_grade()

Conclusion

R6 provides a robust system for object-oriented programming in R. It offers features like encapsulation, inheritance, and reference semantics, making it a powerful tool for creating structured and modular programs in R.

Examples

  1. Introduction to R6 object-oriented programming in R:

    • Overview: Introduce the concept of R6 object-oriented programming.

    • Code:

      # Introduction to R6 object-oriented programming in R library(R6) Person <- R6Class( "Person", public = list( name = NULL, initialize = function(name) { self$name <- name }, greet = function() { cat("Hello, I am", self$name, "\n") } ) ) john <- Person$new("John") john$greet()

  2. Creating and using R6 classes in R programming:

    • Overview: Demonstrate how to create and use R6 classes.

    • Code:

      # Creating and using R6 classes in R programming Animal <- R6Class( "Animal", public = list( name = NULL, initialize = function(name) { self$name <- name }, speak = function() { cat("I am an animal named", self$name, "\n") } ) ) cat <- Animal$new("Cat") cat$speak()

  3. Inheritance and methods in R6 classes:

    • Overview: Illustrate inheritance and methods in R6 classes.

    • Code:

      # Inheritance and methods in R6 classes Dog <- R6Class( "Dog", inherit = Animal, public = list( bark = function() { cat("Woof! Woof!\n") } ) ) dog <- Dog$new("Buddy") dog$speak() dog$bark()

  4. R6 class attributes and methods examples:

    • Overview: Provide examples of attributes and methods in R6 classes.

    • Code:

      # R6 class attributes and methods examples Circle <- R6Class( "Circle", public = list( radius = NULL, initialize = function(radius) { self$radius <- radius }, area = function() { pi * self$radius^2 } ) ) my_circle <- Circle$new(radius = 5) area <- my_circle$area() cat("Area of the circle:", area, "\n")

  5. Encapsulation in R6 programming:

    • Overview: Showcase encapsulation in R6 programming.

    • Code:

      # Encapsulation in R6 programming Counter <- R6Class( "Counter", private = list( value = 0, increment = function() { self$value <- self$value + 1 } ), public = list( get_value = function() { self$value }, increment_and_get = function() { self$increment() self$value } ) ) my_counter <- Counter$new() my_counter$increment_and_get()

  6. Using R6 classes for modular code in R:

    • Overview: Demonstrate how R6 classes can contribute to modular code.

    • Code:

      # Using R6 classes for modular code in R Calculator <- R6Class( "Calculator", public = list( add = function(a, b) { a + b }, multiply = function(a, b) { a * b } ) ) my_calculator <- Calculator$new() result <- my_calculator$add(3, 4) cat("Result of addition:", result, "\n")

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