decorators (version 0.3.0)

validate_arguments: Validate the Type of Input Arguments

Description

Wrap a function with a input validation.

Usage

validate_arguments(func)

Value

(closure) An object that contains the original function bound to the environment of the decorator.

Arguments

func

(function) A function to decorate.

Details

validate_arguments decorator allows the arguments passed to a function to be parsed and validated using the function’s annotations before the function is called.

How It Works

validate_arguments provides an extremely easy way to apply validation to your code with minimal boilerplate. The original function needs to have key-value pairs in its declaration, where the each value carries its designated class.

When to Use It

• To protect functions from receiving unexpected types of input arguments.

• In ValueObjects.

Examples: Functions with Built-in NA classes

Given a Customer ValueObject

Customer <- function(given = NA_character_, family = NA_character_)
    return(data.frame(given = given, family = family))

When Customer is decorated with validate_arguments

Customer <- validate_arguments(Customer)

Then passing arguments of any type other then the declared type prompts an informative error.

In the Customer example, both input arguments given and family are declared as character.

Customer(given = "Bilbo", family = "Baggins") # Works as both arguments are character
#>   given  family
#> 1 Bilbo Baggins
try(Customer(given = "Bilbo", family = 90201)) # Fails because family is not a character
#> Error in Customer(given = "Bilbo", family = 90201) : 
#>   family is of type `numeric` rather than `character`!

References

• Similar Python module

• Closures in R

Examples

Car <- function(model = NA_character_, hp = NA_real_){
    return(data.frame(model = model, hp = hp))
}

Car <- validate_arguments(Car)
try(Car(model = 555, hp = 120)) # fails because model is numeric rather than character