Ruby Array.drop_while Method

By IncludeHelp Last updated : November 28, 2024

In the last articles, we have studied about Array.select and Array.reject methods which give output to the user based on certain conditions. The method Array.drop_while is also a non-destructive method.

Description and Usage

Array.drop_while method works similarly to a loop. As the method, itself contains the word "while" which makes us think that this method is related to a while loop. The operation is just the opposite of while loop. While, while loop works as it processes the things until the condition is not falsified, Array.drop_while method discards or drops the elements until it does not find the element which is specified inside the block. It will print every element if it does not find the element in the Array instance which is defined inside the block of the method. If the specified element lies between two elements of the Array instance, then it will start printing from the greatest one. This method does not through an exception in such a case. It simply drops the elements until it does not find the defined element.

Syntax

Array.drop_while{|var| #condition}

Parameters

This method does not accept any parameter instead a Boolean condition is required inside the block.

Example 1

=begin
    Ruby program to demonstrate Array.drop_while
=end

# array declaration
num = [1,2,3,4,5,6,7,8,9,10,23,11,33,55,66,12]

# user input
puts "Enter the element after which you want to see the result"
lm = gets.chomp.to_i

flag = false
num.each {|nm|
if nm == lm
	flag = true
end
}
if flag == true
    puts "Elements after #{lm} are:"
    puts num.drop_while { |a| a < lm }
else
	puts "Element not found"
end

Output

Enter the element after which you want to see the result
5
Elements after 5 are:
5
6
7
8
9
10
23
11
33
55
66
12

Explanation

In the above code, you can see that this method requires a sequenced Array of elements. It has printed all the elements which are lying after the element 10. Here, first, we have checked the presence of the element in the Array with the help of Array.each then we have carried out the further processing.

Example 2

=begin
    Ruby program to demonstrate Array.drop_while
=end

# array declaration
num = [1,2,3,4,5,6,7,8,9,10,23,11,33,55,66,12]

print num.drop_while{|a|}

Output

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 23, 11, 33, 55, 66, 12]

Explanation

In the above code, you can observe that when you are not specifying any condition inside the method then it is printing every element of the Array object.

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