In ElianHugh/enumr: Static Enumerations

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

library(typed, quietly = TRUE)
library(enumr, quietly = TRUE)

If you are using {typed}, you can make use of the Enum assertion for return and input assertion. Note that enum() is the class definition and Enum() is the type assertion - this matches the {typed} paradigm of assertions (e.g. list() vs typed::List()).

Depending on how you define a variable, you can constrain a variable to either an enum class or enum member. To constrain to an enum class, simply use Enum(). To constrain to an enum member, use Enum(x), with x being an enum.

For instance, let's say we want to ensure that the arguments supplied to a function correspond to an enum member value. Let's create an enum with a list of animals:

my_pets <- enum(
  pet1 = "dog",
  pet2 = "cat",
  pet3 = "goldfish"
)

Now, I want to make a function that only allows the my_pets enum as an argument:

# supply my_pets in the Enum assertion
is_this_my_pet <- ? function(arg = ? Enum(my_pets)) {
    print(arg)
}

# supply an incorrect argument
is_this_my_pet("snake")

# correct arg
is_this_my_pet("dog")