In r-lib/sloop: Helpers for 'OOP' in R

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sloop

The goal of sloop is to provide tools to help you interactively explore and understand object oriented programming in R, particularly with S3.

Please note that unlike other r-lib packages, sloop only works with R 3.3 and later.

Installation

You can install sloop from github with:

# install.packages("pak")
pak::pak("r-lib/sloop")

Usage

library(sloop)

sloop provides a variety of tools for understanding how S3 works. The most useful is probably s3_dispatch(). Given a function call, it shows the set of methods that are considered, found, and actually called:

s3_dispatch(print(Sys.time()))

To the best of my ability it covers all the details of S3 method dispatch including group generics, internal generics, implicit classes, and use of NextMethod() (indicated by ->):

# Implicit class
x <- matrix(1:6, nrow = 2)
s3_dispatch(print(x))

# Internal generic 
length.numeric <- function(x) 10
s3_dispatch(length(x))

s3_dispatch(length(structure(x, class = "numeric")))

# NextMethod
s3_dispatch(Sys.Date()[1])

# group generic + NextMethod()
s3_dispatch(sum(Sys.Date()))

It also provides tools for determing what type of function or object you're dealing with:

ftype(t)
ftype(t.test)
ftype(t.data.frame)

otype(1:10)
otype(mtcars)
otype(R6::R6Class()$new())

And for retrieving the methods associated with a generic or class:

s3_methods_class("factor")

s3_methods_generic("summary")

r-lib/sloop documentation built on Nov. 4, 2023, 4:20 a.m.