Enumerable Module in Ruby

#ruby #rails #enumerable

Ruby's Enumerable module adds magical methods
to classes like Array and Hash.
In this post, we will learn to implement enumeration with an example.

Enumeration

Enumeration is a process of traversing over objects one by one.
To make a class enumerable, we can include Enumerable module.
Thus, giving access to methods like #map, #filter, #count, #include?, #any?, #uniq and a lot more!

#each

Enumerable module maily relies on #each method on the implementing class.
The #each method is implemented such that when a block is passed,
the contents of the collection are evaluated.

> [1, 2, 3].each { |a| a }
=> [1, 2, 3]

Enumerator

Enumerator is a class which allows manual iteration over an enumerator object.
When #each is called without a block, it returns a new Enumerator object
hence allowing to chain multiple enumerators.

> enumerator = %w[foo bar baz].each
> enumerator
=> #<Enumerator: ["foo", "bar", "baz"]:each>

> enumerator.map.with_index { |w, i| "#{i}:#{w}" }
=> ["0:foo", "1:bar", "2:baz"]