Propagating Functionality with Inheritance

Object-Oriented Programming with S3 and R6 in R

Richie Cotton

Data Evangelist at DataCamp

ch4_1-propagating-functionality-with-inheritance.004.png

thing_factory <- R6Class(
  "Thing",
  private = list(
    a_field = "a value",
    another_field = 123
  ),
  public = list(
    do_something = function(x, y, z) {
      # do something here
    }
  )
)

ch4_1-propagating-functionality-with-inheritance.007.png

child_thing_factory <- R6Class(
  "ChildThing",
  inherit = thing_factory

  public = list(
    do_something_else = function() {
      # more functionality
    }
  )

)

ch4_1-propagating-functionality-with-inheritance.012.png

ch4_1-propagating-functionality-with-inheritance.015.png

ch4_1-propagating-functionality-with-inheritance.016.png

a_thing <- thing_factory$new()

class(a_thing)

"Thing" "R6"

inherits(a_thing, "Thing")

TRUE

inherits(a_thing, "R6")

TRUE

a_child_thing <- child_thing_factory$new()

class(a_child_thing)

"ChildThing" "Thing"      "R6"

inherits(a_child_thing, "ChildThing")

TRUE

inherits(a_child_thing, "Thing")

TRUE

inherits(a_child_thing, "R6")

TRUE

Summary

Propagate functionality using inheritance
Use the inherit arg to R6Class()
Children get their parent’s functionality
... but the converse is not true

Let's practice!

Object-Oriented Programming with S3 and R6 in R