README.Rmd

---
output: github_document
---

<!-- README.md is generated from README.Rmd. Please edit that file -->

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.path = "man/figures/README-"
)
```

# sloop <a href="https://sloop.r-lib.org"><img src="man/figures/logo.png" align="right" height="138" alt="sloop website" /></a>

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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](https://github.com/r-lib) packages, sloop only works with R 3.3 and later.

## Installation

You can install sloop from github with:

```{r gh-installation, eval = FALSE}
# install.packages("pak")
pak::pak("r-lib/sloop")
```

## Usage

```{r setup}
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:

```{r}
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 `->`):

```{r}
# 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:

```{r}
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:

```{r}
s3_methods_class("factor")

s3_methods_generic("summary")
```