How To Convert Array To Hash In Ruby

by

In Ruby, arrays and hashes are two essential data structures used to store and manipulate data. Arrays are ordered lists of elements, while hashes are collections of key-value pairs. Sometimes, you may need to convert an array to a hash, and in this blog post, we’ll explore different ways of doing that in Ruby.

1. Using the to_h method

The simplest way to convert an array to a hash is to use the to_h method. This method is only available in Ruby 2.1 or newer. You can call it on an array of key-value pairs (arrays with two elements), and it will return a hash with those key-value pairs.

Here’s an example:


array = [[:a, 1], [:b, 2], [:c, 3]]
hash = array.to_h
puts hash.inspect
# Output: {:a=>1, :b=>2, :c=>3}

2. Using the Hash[] constructor

Another way to convert an array to a hash is to use the Hash[] constructor. It also accepts an array of key-value pairs and returns a hash with those pairs.

Here’s an example:


array = [[:a, 1], [:b, 2], [:c, 3]]
hash = Hash[array]
puts hash.inspect
# Output: {:a=>1, :b=>2, :c=>3}

3. Using the each_with_object method

If your array has a different structure or you want to apply some transformation while converting it to a hash, you can use the each_with_object method. It’s an iterator that allows you to build a new object (in this case, a hash) from the array elements.

Let’s say you have an array of words and you want to create a hash with the words as keys and their lengths as values. Here’s how you can do it with each_with_object:


array = %w[apple banana cherry]
hash = array.each_with_object({}) do |word, h|
  h[word] = word.length
end
puts hash.inspect
# Output: {"apple"=>5, "banana"=>6, "cherry"=>6}

4. Using the zip method

If you have two separate arrays (one for keys and one for values) and you want to combine them into a hash, you can use the zip method. It interleaves the elements of two or more arrays so that the values from the corresponding positions are combined into new arrays.

Here’s an example:


keys = [:a, :b, :c]
values = [1, 2, 3]
pairs = keys.zip(values)
hash = pairs.to_h
puts hash.inspect
# Output: {:a=>1, :b=>2, :c=>3}

In this case, we used the zip method to create an array of key-value pairs and then used the to_h method to convert it to a hash.

Conclusion

In this blog post, we’ve looked at several different ways to convert arrays to hashes in Ruby, including using the to_h method, the Hash[] constructor, the each_with_object iterator, and the zip method. Choose the method that best fits your use case and enjoy the flexibility and power of Ruby’s data structures!