R6 classes in R Programming - Step-by-Step Execution

Concept Flow - R6 classes

Define R6 Class

↓

Create Object (Instance)

↓

Call Methods

↓

Modify or Access Fields

↓

Use or Update Object State

↓

End or Reuse Object

This flow shows how you define an R6 class, create an object, call its methods, and access or modify its fields step-by-step.

Execution Sample

R Programming

library(R6)
Person <- R6Class("Person",
  public = list(
    name = NULL,
    initialize = function(name) { self$name <- name },
    greet = function() { paste0("Hello, ", self$name) }
  )
)
p <- Person$new("Alice")
p$greet()

This code defines a Person class with a name field and greet method, creates an instance named Alice, and calls greet.

Execution Table

Step	Action	Evaluation	Result
1	Load R6 library	library(R6)	R6 functions available
2	Define Person class	R6Class("Person", ...)	Class Person created
3	Create object p	Person$new("Alice")	Object p with name='Alice'
4	Call p$greet()	p$greet()	"Hello, Alice"
5	End	No more commands	Execution stops

💡 No more commands to execute, program ends

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
p$name	NULL	"Alice"	"Alice"	"Alice"
p$greet()	Function	Function	Function	Function

Key Moments - 2 Insights

Why do we use self$name inside methods instead of just name?

Inside methods, self$name refers to the object's field. Using just name would look for a local variable, which does not exist. See Step 4 in execution_table where self$name is used.

What happens when we call Person$new("Alice")?

It creates a new object p and runs initialize, setting p$name to "Alice". See Step 3 in execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of p$name after Step 3?

A "Hello, Alice"

B NULL

C "Alice"

D Function

💡 Hint

Check the 'Result' column in Step 3 of execution_table.

At which step does the greet method return the greeting string?

A Step 4

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Evaluation' and 'Result' columns in Step 4.

If we change initialize to set self$name <- "Bob", what will p$greet() return?

A "Hello, Alice"

B "Hello, Bob"

C NULL

D Error

💡 Hint

Refer to how initialize sets self$name in Step 3 and greet uses self$name in Step 4.

Concept Snapshot

R6 classes in R create objects with fields and methods.
Use R6Class() to define a class.
$new() creates an instance.
Use self$field inside methods to access fields.
Call methods with $ like obj$method().

Full Transcript

This visual execution shows how R6 classes work in R. First, we load the R6 library to get the tools. Then we define a class called Person with a field name and methods initialize and greet. When we create an object p with Person$new("Alice"), the initialize method sets p$name to "Alice". Calling p$greet() returns the string "Hello, Alice" by accessing self$name inside the method. The variable tracker shows how p$name changes from NULL to "Alice" after creation and stays the same after greeting. Key moments clarify why self$name is needed inside methods and what happens during object creation. The quiz tests understanding of variable values at each step and the effect of changing initialize. This step-by-step trace helps beginners see how R6 classes create and use objects in R.