The Object Factory Object-Oriented Programming in R: S3 & R6 - - PowerPoint PPT Presentation

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Dec 04, 2023 338 likes •608 views

OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6 The Object Factory Object-Oriented Programming in R: S3 & R6 pour refill Object-Oriented Programming in R: S3 & R6 class generators are templates for objects a.k.a. factories

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6

The Object Factory

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Object-Oriented Programming in R: S3 & R6

pour refill

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Object-Oriented Programming in R: S3 & R6

class generators are templates for objects a.k.a. factories

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Object-Oriented Programming in R: S3 & R6

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Object-Oriented Programming in R: S3 & R6

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Object-Oriented Programming in R: S3 & R6

library(R6) thing_factory <- R6Class( "Thing", ) private = list( a_field = "a value", another_field = 123 )

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Object-Oriented Programming in R: S3 & R6

Coming soon…

public active

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Object-Oriented Programming in R: S3 & R6

> a_thing <- thing_factory$new() > another_thing <- thing_factory$new() > yet_another_thing <- thing_factory$new()

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Object-Oriented Programming in R: S3 & R6

Summary

Load the R6 package to work with R6!
Define class generators with R6Class()
Class names should be UpperCamelCase
Data fields stored in private list
Create objects with factory’s new() method

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6

Let’s practice!

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6

Hiding Complexity with Encapsulation

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Object-Oriented Programming in R: S3 & R6

Encapsulation

implementation user interface

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Object-Oriented Programming in R: S3 & R6

microwave_oven_factory <- R6Class( "MicrowaveOven", private = list( power_rating_watts = 800, ), ) public = list( ) private$door_is_open <- TRUE

pen_door = function() {

} door_is_open = FALSE

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Object-Oriented Programming in R: S3 & R6

private$ accesses private elements self$ accesses public elements

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Object-Oriented Programming in R: S3 & R6

Summary

Encapsulation = separating implementation from UI
Store data in private list
Store methods in public list
Use private$ to access private elements
…and self$ to access public elements

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6

Let’s practice!

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6

Geing and Seing with Active Bindings

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Object-Oriented Programming in R: S3 & R6

Part# S-0896

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Object-Oriented Programming in R: S3 & R6

geing = read the data field seing = write the data field

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Object-Oriented Programming in R: S3 & R6

Active Bindings

defined like functions accessed like data variables

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Object-Oriented Programming in R: S3 & R6

thing_factory <- R6Class( "Thing", private = list( ..a_field = "a value", ..another_field = 123 ), active = list( a_field = function() { if(is.na(private$..a_field)) { return("a missing value") } private$..a_field }, another_field = function(value) { if(missing(value)) { private$..another_field } else { private$..another_field <- value } } ) ) assert_is_a_number(value)

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Object-Oriented Programming in R: S3 & R6

> a_thing <- thing_factory$new() > a_thing$a_field [1] "a value" > a_thing$a_field <- "a new value" Error in (function (value) : a_field is read-only.

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Object-Oriented Programming in R: S3 & R6

> a_thing$another_field <- 456 > a_thing$another_field <- "456" Error in (function (value) : is_a_number : value is not of class 'numeric'; it has class 'character'.

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Object-Oriented Programming in R: S3 & R6

Summary

Control private access with active bindings
Defined like functions
Accessed like data
Use assertive to check binding inputs

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OBJECT-ORIENTED PROGRAMMING IN R: S3 & R6