Ruby Arrays

Arrays are ordered collections that can hold elements of any data type, including numbers, strings, other arrays, or even objects.

ages = [10, 12, 3, 40, 5]
puts ages.inspect

# Output
# [10, 12, 3, 40, 5]

Creating an Array

In Ruby, you can create an array by enclosing a list of elements in square brackets ([]).

For instance, to store the names of students in a class, you'd write:

student_names = ["Alice", "Bob", "Charlie"]

student_names1 = []
student_names2 = Array.new

Printing an Array

You can print an array in the following ways:

1. Using the .inspect method.

The .inspect method returns a string representation of an object, i.e., how Ruby internally represents the object. For example,

student_names = ["Alice", "Bob", "Charlie"]

puts student_names.inspect

# Output: ["Alice", "Bob", "Charlie"]

As you can see, Ruby internally represents the student_names array as ["Alice", "Bob", "Charlie"].

print student_names
p student_names

2. Using puts without .inspect.

You can use puts without .inspect if you want to print each element in a new line. For example,

student_names = ["Alice", "Bob", "Charlie"]

puts student_names

Output

Alice
Bob
Charlie

Accessing Array Elements

Once an array is created, you can access its elements by their indexes.

The index of an array starts from 0, meaning the first element is at index 0, the second at index 1, and so on. For example,

Example

fruits = ["apple", "banana", "cherry"]

first_fruit = fruits[0]   
second_fruit = fruits[1]  

puts first_fruit
puts second_fruit

Output

apple
banana

Operations in an Array

You can perform various operations on an array, such as adding, removing, and changing its elements.

Let's see each of the operations in detail.

Adding Elements to an Array

You can use the push method to add one or more elements to the end of an array. For example,

fruits = ["apple", "banana", "cherry"]

# Add "orange" to the end of the array
fruits.push("orange")

puts fruits.inspect

Output

["apple", "banana", "cherry", "orange"]

You can also use a shovel operator (<<) to add one or more elements to the end of an array. For example,

fruits = ["apple", "banana", "cherry"]
fruits << "mango" << "pineapple"

puts fruits.inspect

Output

["apple", "banana", "cherry", "mango", "pineapple"]

Removing Elements From an Array

You can use the pop method to remove the last element from an array. For example,

fruits = ["apple", "banana", "cherry"]
last = fruits.pop     

puts fruits.inspect
puts last

Output

["apple", "banana"]
cherry

As you can see, the pop method removes the last element and returns it. We then stored this returned value in the last variable.

Changing Elements in an Array

You can change an element in an array by assigning a new value to the specified index. For example,

fruits = ["apple", "banana", "cherry"]
puts "Before changing, the second element is: #{fruits[1]}"

fruits[1] = "mango"

puts "After changing, the second element is: #{fruits[1]}"

Output

Before changing, the second element is banana  
After changing, the second element is mango

Array Methods

There are several other array methods you can use to perform various operations. These methods are summarized in the table below:

Example: Array Methods

Let's look at an example to see how some of the above methods work.

array1 = [1, 2, 3]
array2 = [4, 5, 6]

# Use concat to merge array1 and array2
combined_array = array1.concat(array2)
puts "Combined Array: #{combined_array.inspect}"

# Use index to find the index of element 5 in combined_array
index = combined_array.index(5)
puts "Index of 5: #{index}"

# Use slice to get a portion of combined_array (elements from index 1 to 3)
sliced_array = combined_array.slice(1, 3)
puts "Sliced Array: #{sliced_array.inspect}"

# Use slice! to remove two elements starting from index 3 
combined_array.slice!(3, 2)
puts "Array After Removing 4 and 5: #{combined_array.inspect}"

# Use insert to add elements 7, 8 at index 3
combined_array.insert(3, 7, 8)
puts "Array After Inserting 7 and 8: #{combined_array.inspect}"

Output

Combined Array: [1, 2, 3, 4, 5, 6]
Index of 5: 4
Sliced Array: [2, 3, 4]
Array After Removing 4 and 5: [1, 2, 3, 6]
Array After Inserting 7 and 8: [1, 2, 3, 7, 8, 6]

empty_array = Array.new

# Creates an array with 5 empty slots
array_with_size = Array.new(5)

# Array with 4 elements
# Each element has 0 as a value
array_with_elements = Array.new(4,0)

arr = Array.new(4) { |i| [1, 2, 3, 4][i] }

fruits = ["apple", "banana", "cherry"]
puts fruits[-1]  # Output: cherry
puts fruits[-2]  # Output: banana

fruits = ["apple", "banana", "cherry"]

# Add "strawberry" to the beginning of the array
fruits.unshift("strawberry")

puts fruits.inspect

# Output: ["strawberry", "apple", "banana", "cherry"]

fruits = ["apple", "banana", "cherry"]
first = fruits.shift  

puts fruits.inspect
puts first

["banana", "cherry"]
apple