Arrays in Ruby

Ruby arrays are ordered collections of objects. They can hold objects like integer, number, hash, string, symbol or any other array.

An array is a list of values, objects, enclosed in square brackets and separated by commas.

Each element in an array is referred to by an index which starts at 0 like in C. A negative index is assumed to be relative to the end of the array i.e., -1 indicates the last element of the array, -2 is the 2nd last element and so on.

Creating Arrays

The two common ways to create arrays are:

• Using square brackets

  fruits = ['mango', 'banana', 'apple'] # output: fruits array with three fruits name
  

• Using Array.new

  numbers = Array.new(3, 0) # output: numbers array with 3 elements initialized to 0
  puts numbers # [0, 0, 0]
  
  languages = Array.new(5, 'ruby')
  puts languages # ['ruby', 'ruby', 'ruby', 'ruby', 'ruby]
  

This approach is quite useful in creating an array with some default values.

Accessing element in Array

You can access an element of an array by using its index value.

fruits = ['mango', 'banana', 'apple']
puts fruits[0] # output: 'mango'

Accessing multiple elements

One can access multiple elements as well. It can be achieved by passing two indices.

languages = ['C', 'Ruby', 'Python', 'Go']
high_level = languages[1, 3]
puts high_level # ["Ruby", "Python", "Go"]

Adding an element to an Array

If you want to add a new element to Array, you can achieve that through the following methods.

• push method:

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.push('JavaScript')
  puts languages # ['C', 'Ruby', 'Python', 'Go', 'JavaScript']
  

• Using the << operator:

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages << 'JavaScript'
  puts languages # ['C', 'Ruby', 'Python', 'Go', 'JavaScript']
  

• If you want to add to the beginning, use the unshift method:

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.unshift('JavaScript')
  puts languages # ['JavaScript', 'C', 'Ruby', 'Python', 'Go']
  

Removing an element from an Array

Similar to addition, Ruby provide many methods to remove element from an Array. Following are a few methods:

• delete method: It will delete the occurrences of the specified element from array.

  languages = ['C', 'Ruby', 'Python', 'Go', 'C']
  languages.delete('C')
  puts languages # ['Ruby', 'Python', 'Go']
  

• delete_at method: Delete the element at the specified index.

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.delete_at(2)
  puts languages # ['C', 'Ruby', 'Go']
  

• pop method: It is used to remove the element from end of the array.

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.pop
  puts languages # ['C', 'Ruby', 'Python']
  

• shift method: Removes the first element from the array.

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.shift
  puts languages # ['Ruby', 'Python', 'Go']
  

Iterating over an Array

There are many ways we can iterate over an Array.

• each method is the most common way to iterator over an Array.

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.each do |language|
    puts "#{language} is nice."
  end
  
  # output
  C is nice.
  Ruby is nice.
  Python is nice.
  Go is nice.
  

  NOTE: Method each_index will only give index instead of element.

• each_with_index method provides you an index along with element while iterating over Array.

  languages = ['C', 'Ruby', 'Python', 'Go']
  languages.each_with_index do |language, i|
    puts "#{i + 1}. #{language} is nice."
  end
  
  # output
  1. C is nice.
  2. Ruby is nice.
  3. Python is nice.
  4. Go is nice.
  

Comparing Arrays

You can compare two arrays for equality using the == operator.

language1 = ['C', 'Ruby', 'Python', 'Go']
language2 = ['C', 'Ruby', 'Python', 'Go']
puts language1 == language2 # true

language2.delete('C')
puts language1 == language2 # false

Common Array methods

include?

This method checks whether the argument given is included in the array or not.

languages = ['C', 'Ruby', 'Python', 'Go']
puts languages.include?('Ruby') # true

sort

This method sorts the Array elements.

languages = ['C', 'Ruby', 'Python', 'Go']
puts languages.sort # ["C", "Go", "Python", "Ruby"]

sort!

This method sorts the Array elements in place. Notice the ! to indicate “dangerous”.

languages = ['C', 'Ruby', 'Python', 'Go']
languages.sort!
puts languages      # ["C", "Go", "Python", "Ruby"]

concat

This method will concat another method with the existing one.

languages = ['C', 'Ruby', 'Python', 'Go']
updated = languages.concat(['Rust', 'Dart'])
puts updated # ["C", "Ruby", "Python", "Go", "Rust", "Dart"]

NOTE: You can see all Array methods in their official documentation here. Go through it and familiarize yourself. There are many handy methods available.