Kalpit
Kalpit Full stack developer working on Ruby on Rails and React

Transform hash value(s) in Ruby

Transform hash value(s) in Ruby

In order to transform or change hash values in ruby, generally we use map or each_with_obejct or inject

If you’re using Ruby 2.4+, we can use a method called transform_values instead of map or any other methods.

In this blog post, we will explore examples of using the map, each_with_object, inject, and transform_values methods to change hash values.

There are two main ways to change hash values: directly modifying the existing hash, or returning a new hash with transformed values without modifying the original.

Example 1: Return multiple of 2 of each value in the hash

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

hash = { one: 1, two: 2, three: 3, four: 4, five: 5 }

# map
hash.map { |key, value| [key, value * 2] }.to_h

# each_wth_object
transformed_hash = hash.each_with_object({}) do |(key, value), new_hash|
	new_hash[key] = value * 2
end

# inject
hash.inject({}) do |new_hash, (key, value)|
	new_hash[key] = value * 2
	new_hash
end

# transform_values
hash.transform_values { |value| value * 2 }

# If we want to change the hash value, use `!` with transform_values
hash.transform_values! { |value| value * 2 }

Let’s consider an example where the user wants to capitalize the first letter of a string in a hash. There are multiple ways to achieve this, as shown below.

Example 2: Return capitalize the value

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

hash = {
	first_name: 'luca',
	last_name: 'brasi',
	test: 3
}

# map
hash = hash.map { |key, value| value.capitalize }

# each_with_object
hash.each_with_object({}) { |(key, value), hash| hash[key] = value.capitalize }

# inject
hash = hash.inject({}) do |new_hash, (key, value)|
	new_hash[key] = value.capitalize
	new_hash
end

# transform_values
hash = hash.transform_values { |value| value.capitalize }

# If we want to change the hash value, use `!` with transform_values
hash.transform_values! { |value| value.capitalize }

comments powered by Disqus