A collection of helper functions designed to help you to better understand object oriented programming in R, particularly using 'S3'.
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.
You can install sloop from github with:
# install.packages("devtools")devtools::install_github("r-lib/sloop")
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()))#> => print.POSIXct#> print.POSIXt#> * print.default
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 classx <- matrix(1:6, nrow = 2)s3_dispatch(print(x))#> print.matrix#> print.integer#> print.numeric#> => print.default# Internal genericlength.numeric <- function(x) 10s3_dispatch(length(x))#> length.matrix#> length.integer#> * length.numeric#> length.default#> => length (internal)s3_dispatch(length(structure(x, class = "numeric")))#> => length.numeric#> length.default#> * length (internal)# NextMethods3_dispatch(Sys.Date()[1])#> => [.Date#> [.default#> -> [ (internal)# group generic + NextMethod()s3_dispatch(sum(Sys.Date()))#> sum.Date#> sum.default#> => Summary.Date#> Summary.default#> -> sum (internal)
It also provides tools for determing what type of function or object you’re dealing with:
ftype(t)#> [1] "S3" "generic"ftype(t.test)#> [1] "S3" "generic"ftype(t.data.frame)#> [1] "S3" "method"otype(1:10)#> [1] "base"otype(mtcars)#> [1] "S3"otype(R6::R6Class()$new())#> [1] "R6"
And for retrieving the methods associated with a generic or class:
s3_methods_class("factor")#> # A tibble: 27 x 4#> generic class visible source#> <chr> <chr> <lgl> <chr>#> 1 [ factor TRUE base#> 2 [[ factor TRUE base#> 3 [[<- factor TRUE base#> 4 [<- factor TRUE base#> 5 all.equal factor TRUE base#> 6 as.character factor TRUE base#> 7 as.data.frame factor TRUE base#> 8 as.Date factor TRUE base#> 9 as.list factor TRUE base#> 10 as.logical factor TRUE base#> # … with 17 more rowss3_methods_generic("summary")#> # A tibble: 36 x 4#> generic class visible source#> <chr> <chr> <lgl> <chr>#> 1 summary aov TRUE stats#> 2 summary aovlist FALSE registered S3method#> 3 summary aspell FALSE registered S3method#> 4 summary check_packages_in_dir FALSE registered S3method#> 5 summary connection TRUE base#> 6 summary data.frame TRUE base#> 7 summary Date TRUE base#> 8 summary default TRUE base#> 9 summary ecdf FALSE registered S3method#> 10 summary factor TRUE base#> # … with 26 more rows
sloop has a website: http://sloop.r-lib.org/ !
s3_methods_generic()
returns correct character class with recent
versions of the tibble package (#19)
s4_methods_class()
returns 0 rows instead of an error if no
methods are found (#18).