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Array.unshift() Method with Example in Ruby

Ruby Array.unshift() Method: Here, we are going to learn about the Array.unshift() Method with examples in Ruby programming language.
Submitted by Hrithik Chandra Prasad, on February 15, 2020

Array.unshift() Method

In this article, we will study about Array.unshift() Method. You all must be thinking the method must be doing something which is related to unshifting of objects in the Array instance. It is not as simple as it looks. Well, we will figure this out in the rest of our content. We will try to understand it with the help of syntax and demonstrating program codes.

Method description:

This method is a public instance method and defined for the Array class in Ruby's library. This method works in a way that affixes the object which is provided with the method at the time of its invocation to the front of the self Array object. It simply means that the object will be shifted to the 0th index and the indices of rest objects are incremented by one. You can provide more than one argument to the method at the time of its invocation. This method is one of the examples of destructive methods where the changes created by the method are permanent. There is no non-destructive version of this method.

Syntax:

    array_instance.unshift(object) -> array

Argument(s) required:

This method can take n number of objects. You can even provide an Array instance as the argument.

Example 1:

=begin
  Ruby program to demonstrate unshift method
=end

# array declaration
table = [2,4,8,10,12,134,160,180,200,344]

puts "Array unshift implementation"

puts "Enter the number of objects you want to add:"
num = gets.chomp.to_i

for i in 1..num
	puts "Enter the object:"
	ele = gets.chomp
	table.unshift(ele)
end

puts "The final Array instance: #{table}"

Output

Array unshift implementation
Enter the number of objects you want to add:
 3
Enter the object:
 Hrithik
Enter the object:
 Amisha
Enter the object:
 Satyam
The final Array instance: ["Satyam", "Amisha", "Hrithik", 2, 4, 8, 10, 12, 134, 160, 180, 200, 344]

Explanation:

In the above code, you can observe that we are adding elements in the Array instance with the help of the Array.unshift() method. In the output, you can see that the objects which are given by the user are stored from 0^th index. The previously present elements are moved upward.

Example 2:

=begin
  Ruby program to demonstrate unshift method
=end

# array declaration
table = [2,4,8,10,12,134,160,180,200,344]

puts "Array unshift implementation"
Name = ["Ayush","Saksham","Nikhil"]

table.unshift(Name)

puts "The final Array instance: #{table}"

Output

Array unshift implementation
The final Array instance: [["Ayush", "Saksham", "Nikhil"], 2, 4, 8, 10, 12, 134, 160, 180, 200, 344]

Explanation:

In the above code, you can observe that we have prepended an Array instance in the self Array. Now, it has become a subarray of the self Array which is stored at the 0^th index of the self Array.