Ruby Common Array Methods


title: Common Array Methods

Common Array Methods

Arrays are a core foundation of programming in Ruby and most languages. Arrays are so common that it is beneficial to know, and even memorize, some of their most commonly used methods. If you want to know more about Ruby Arrays, we have an article about them.

For the purpose of this guide, our array will be as follows:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4]

.length

The .length method tallies the number of elements in the array and returns the count:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.length => 5

This is also similar to .count and .size methods.

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.count => 5 array.size => 5

.first

The .first method returns the first element of the array, the element at index 0:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.first => 0

.last

The .last method returns the last element of the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.last => 4

.take

The .take method returns the first n elements of the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.take(3) => [0, 1, 2] array => [0, 1, 2, 3, 4]

.drop

The .drop method returns the elements after n elements of the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.drop(3) => [3, 4] array => [0, 1, 2, 3, 4]

array index

You can return a specific element in an array by accessing its index. If the index does not exist in the array, nil will be returned:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array[2] => 2 array[5] => nil

.pop

The .pop method will permanently remove the last element of an array and return this element:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.pop => 4 array => [0, 1, 2, 3]

.shift

The .shift method will permanently remove the first element of an array and return this element:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.shift => 0 array => [1, 2, 3, 4]

.push

The .push method will add an element to the end of an array and return the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.push(99) => [0, 1, 2, 3, 4, 99] array => [0, 1, 2, 3, 4, 99]

.unshift

The .unshift method adds an element to the beginning of an array and return the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.unshift(99) => [99, 0, 1, 2, 3, 4] array => [99, 0, 1, 2, 3, 4]

.delete

The .delete method removes a specified element from an array permanently and return the element:

array = [1, 2, 3, 4, 5] => [1, 2, 3, 4, 5] array.delete(3) => 3 array => [1, 2, 4, 5]

.delete_at

The .delete_at method permanently removes an element of an array at a specified index and return the element:

array = [1, 2, 3, 4, 5] => [1, 2, 3, 4, 5] array.delete_at(3) => 3 array => [1, 2, 3, 5]

.reverse

The .reverse method returns a new array that includes the elements of the original array but in reverse order:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] new_array = array.reverse => [4, 3, 2, 1, 0] new_array => [4, 3, 2, 1, 0] array => [0, 1, 2, 3, 4]

.select

The .select method iterates over an array and returns a new array that includes any items that return true to the expression provided:

array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] new_array = array.select { |number| number > 4 } => [5, 6, 7, 8, 9, 10] new_array => [5, 6, 7, 8, 9, 10] array => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

.include?

The .include? method checks to see if the argument given is included in the array and returns true if it is:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.include?(3) => true array.include?(5) => false

.flatten

The .flatten method can be used to take an array that contains nested arrays and create a one-dimensional array:

array = [1, 2, [3, 4, 5], [6, 7]] => [1, 2, [3, 4, 5], [6, 7]] new_array = array.flatten => [1, 2, 3, 4, 5, 6, 7] new_array => [1, 2, 3, 4, 5, 6, 7] array => [1, 2, [3, 4, 5], [6, 7]]

.join

The .join method returns a string of all the elements of the array separated by a separator parameter. If the separator parameter is nil, the method uses an empty string as a separator between strings:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.join => "01234" array.join("*") => "0*1*2*3*4" array => [0, 1, 2, 3, 4]

.each

The .each method iterates over each element of the array, allowing you to perform actions on them:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.each { |element| puts element } => 0 1 2 3 4 array => [0, 1, 2, 3, 4]

.map

The .map method is the same as the .collect method. The .map and .collect methods iterate over each element of the array, allowing you to perform actions on them. The .map and .collect methods differ from the .each method in that they return an array containing the transformed elements:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] new_array = array.map { |element| element * 2 } => [0, 2, 4, 6, 8] new_array => [0, 2, 4, 6, 8] array => [0, 1, 2, 3, 4]

.uniq

The .uniq method returns a copy of the array containing only unique elements. Any duplicate elements are removed from the array. The original array is not modified.

array = [1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 6, 7, 8] => [1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 6, 7, 8] new_array = array.uniq => [1, 2, 3, 4, 5, 6, 7, 8] new_array => [1, 2, 3, 4, 5, 6, 7, 8] array => [1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 6, 7, 8]

.concat

The .concat method appends the elements from an array to the original array. The .concat method can take in multiple arrays as an argument, which will in turn append multiple arrays to the original array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.concat([5, 6, 7], [8, 9, 10]) => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] array => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

.clear

The .clear method will delete all the data in the array:

array = [0, 1, 2, 3, 4] => [0, 1, 2, 3, 4] array.clear => [] array => []

More Information

This article needs improvement. You can help improve this article. You can also write similar articles and help the community.