Mixin in R

In R, mixins are used to combine functionality from multiple classes through inheritance. To use a mixin in R, you need to create a new class that inherits both from the base class and the mixin class. Here's an example:

# define the mixin class
my_mixin <- setRefClass("MyMixin", methods = list(
  say_hello = function() {
    cat("Hello, world!\n")
  }
))
# define the base class

my_base <- setRefClass("MyBase", methods = list(

  my_method = function() {

    cat("This is my method\n")

  }

))
# define the new class that inherits from both the base class and the mixin class

my_class <- setRefClass("MyClass", contains = c("MyBase", "MyMixin"))
# create an instance of the new class and call methods from both the base class and mixin class

obj <- my_class$new()

obj$my_method()

obj$say_hello()

In this example, we first define the MyMixin class with a single method say_hello. We also define the MyBase class with a single method my_method. Then, we create a new class MyClass that inherits from both MyBase and MyMixin. Finally, we create an instance of the MyClass and call both my_method and say_hello on the instance.

Mixins are useful when you want to add a small piece of functionality to a class without modifying its interface or creating a new subclass.