Keyword arguments in Ruby 2.0

Intro

The first stable release of Ruby 2.0 has arrived and I'm checking out some of the added features.

With this post I'm checking out keyword arguments. Wikipedia defines as

a computer language's support for function calls that clearly state the name of each parameter within the function call itself.

Before we get into that let's look at a couple other examples of Ruby methods with parameters.

Traditional method with parameters

First there's the traditional method with arguments.

def create_profile(first_name, last_name)
  puts "first name: #{first_name}" 
  puts "last name: #{last_name}" 
end

create_profile 'Carlos', 'Cardona'
# first name: Carlos
# last name: Cardona

Nothing special here except to note if you pass in the wrong number of arguments at the function call you'll get an error like so

create_profile 'Cardona'
# ArgumentError: wrong number of arguments (1 for 2)

Method with default parameter values

You can defend against that with default parameter values

def create_profile(first_name = "n/a", last_name = "n/a")
  puts "first name: #{first_name}"
  puts "last name: #{last_name}"
end

create_profile 'Cardona'
# first name: Cardona
# last name: n/a

Ok that prevented the ArgumentError but it incorrectly passed in Cardona as the first_name argument and not the second_name argument. And that is where keyword arguments really shine.

Method with Keyword Arguments and default parameter values

Here you can see that we can pass in our arguments with a keyword. This allows us to be more confident that our default parameter values will get assigned correctly.

def create_profile(first_name: "n/a", last_name: "n/a")
  puts "first name: #{first_name}"
  puts "last name: #{last_name}"
end

create_profile last_name: 'Cardona'
# first name: n/a
# last name: Cardona

At the same time it allows us to pass in arguments in a different order than they were defined which makes the function call more fluid.

create_profile last_name: 'Cardona', first_name: 'Carlos'
# first name: Carlos
# last name: Cardona

Published

Tags

• ruby 7
• code 21