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Hash.transform_keys Method with Example in Ruby

Ruby Hash.transform_keys Method: Here, we are going to learn about the Hash.transform_keys Method with examples in Ruby programming language.
Submitted by Hrithik Chandra Prasad, on March 14, 2020

Hash.transform_keys Method

In this article, we will study about Hash.transform_keys Method. The working of this method can be predicted with the help of its name but it is not as simple as it seems. Well, we will understand this method with the help of its syntax and program code in the rest of the content.

Method description:

This method is a public instance method that is defined in the ruby library especially for Hash class. This method works in a way that it runs the provided block at least once for each hash key and returns a new hash. An enumerator will be returned if you are not providing any block along with the method at the time of its invocation.

This method does not bring change in the actual hash because this method belongs to the category of non-destructive methods.

Syntax:

    Hash_object.transform_keys
    or
    Hash_object.transform_keys{|key| block}

Argument(s) required:

This method does not accept any parameter instead you can provide a block for a better implementation.

Example 1:

=begin
  Ruby program to demonstrate transform_keys method
=end	

hash1={"color"=>"Black","object"=>"car","love"=>"friends","fruit"=>"Kiwi","vege"=>"potato"}

puts "Hash transform_keys implementation"

hsh = hash1.transform_keys{|key| key+key}

puts  "Value hash is #{hsh}"

puts "Self hash object : #{hash1}"

Output

Hash transform_keys implementation
Value hash is {"colorcolor"=>"Black", "objectobject"=>"car", "lovelove"=>"friends", "fruitfruit"=>"Kiwi", "vegevege"=>"potato"}
Self hash object : {"color"=>"Black", "object"=>"car", "love"=>"friends", "fruit"=>"Kiwi", "vege"=>"potato"}

Explanation:

In the above code, you can observe that we are updating the keys of the hash object with the help of the Hash.transform_keys() method. You can see that all the keys are updated by their names. This method is not creating changes in the actual hash object because this method is one of the examples of non-destructive methods.

Example 2:

=begin
  Ruby program to demonstrate transform_keys method
=end	

hash1={"color"=>"Black","object"=>"car","love"=>"friends","fruit"=>"Kiwi","vege"=>"potato"}

puts "Hash transform_keys implementation"

hsh = hash1.transform_keys

puts  "Value hash is #{hsh}"

puts "Self hash object : #{hash1}"

Output

Hash transform_keys implementation
Value hash is #<Enumerator:0x00005610dc177dc8>
Self hash object : {"color"=>"Black", "object"=>"car", "love"=>"friends", "fruit"=>"Kiwi", "vege"=>"potato"}

Explanation:

In the above code, you can observe that when we are invoking the method without passing any block then the method is returning an enumerator.