Ruby Enumerable and Comparable

Prerequisites

• Ruby Enumerable Builtins
• Ruby Object

Objectives

By the end of this talk, developers should be able to:

• Add Comparable operators to a class.
• Add Enumerable methods to a class.

Preparation

1. Fork and clone this repository. FAQ
2. Create a new branch, training, for your work.
3. Checkout to the training branch.
4. Install dependencies with bundle install.

Introduction

We'll explore an important Ruby mechanism for adding behavior to a class: mixins.

The Comparable Module

Lab - comparing cards

How do you compare cards?

In your squads create an algorithm to determine which of two cards, if either, is "greater" than the other.

Demo - A Card Model

The Comparable module provide common operators to a class that implements the <=> (spaceship) operator. Let's look at lib/card.rb.

Adding the spaceship operator to Card.

Lab - A list as a deck of cards

Let's simulate Enumerable methods using a deck of cards. In your squad, one of you will act as the method and another as the block. The third squad member will record the result.

Demo - A Deck Model

Let's explore the start of writing a card game in Ruby using lib/card.rb and lib/deck.rb.

Private methods

It's a best practice to keep our exposed API as small as necessary. I like to keep methods private by default (just like data is) by decorating them with the private method. This makes them uncallable outside the class definition. For example:

class Foo
  def bar
    "baz"
  end
  private :bar

  def qux
    bar # this works
  end
end

Foo.new.bar # this does not work

The Enumerable Module

We'll build our own list using Ruby's Enumerable module.

Code along - Stepped Range

We'll build a new range class that increments by a provided value. The key to creating an Enumerable class is a correct implementation of the each method.

Tasks

Developers should run these often!

• bin/rake nag (or bundle exec rake nag): runs code quality analysis tools on your code and complains.
• bin/rake test (or bundle exec rake test): runs automated tests.

Additional Resources

• List ADT

License

1. All content is licensed under a CC­BY­NC­SA 4.0 license.
2. All software code is licensed under GNU GPLv3. For commercial use or alternative licensing, please contact legal@ga.co.