Ruby Enumerable Cheat Sheet

Ruby Enumerable Cheat Sheet

Most Common Enumerable Methods

#inject / #reduce : The #inject and #reduce methods are interchangeable. Their purpose is to iterate over a collection of data - an array, a range, or any other class that implements an #each method - and return a single value. For example, we can easily sum up a range of integers using (5..10).inject(:+) => 45.

#map : The #map and #collect enumerable methods are interchangeable. They create a new array which, for each element in the original array, contains the values returned by the block. For example, if we have an array of integers, we can easily double each number using [1, 2, 3, 4].map {|integer| integer * 2}.

#select : The #select and #find_all methods are interchangeable. These elements will iterate over each element in a collection of data, and return only those elements that return true from a block. For example [1, 2, 3, 4, 5].select {|integer| integer.even?} => [2, 4].

#sort : The #sort method returns an array of the sorted elements. The sort works by using a comperator <=>. By passing in a block, we can sort the elements by different properties (such as length, for example), and we can indicate if we want the items returned in ascending or descending order.