Using the to_h Method of Array in Ruby

In this blog post, I will explain how to use the to_h method of Array in Ruby. The to_h method converts an array into a hash, where each element of the array becomes a key-value pair in the hash. This method is available in Ruby 2.1 or newer.

There are two ways to use the to_h method: with or without a block.

Without a Block

If you don’t pass a block to the method, then the array must be an array of arrays, each with two elements: the key and the value. For example:

array = [[:foo, :bar], [1, 2], ["hello", "world"]]
hash = array.to_h
puts hash.inspect
# => {:foo=>:bar, 1=>2, "hello"=>"world"}

In this example, the array consists of nested arrays, where each nested array represents a key-value pair. When to_h is called on the array, it converts the array into a hash, where the first element of each nested array becomes a key, and the second element becomes the corresponding value.

It’s important to note that the to_h method raises an error if the array elements are not in the expected key-value pair format. Each element should be an array with exactly two elements: the key and the value.

array = [[:name, "Neo"], :age, 30]
hash = array.to_h
# Raises an error: TypeError (wrong element type Symbol at 1 (expected array))

In this example, the second element :age is not in the key-value pair format, causing a TypeError to be raised.

With a Block

If you pass a block to the method, then you can transform each element of the array into a key-value pair by returning an array with two elements from the block. For example:

array = ["apple", "kiwi", "carrot"]
hash = array.to_h {|item| [item.length, item]}
puts hash.inspect
# => {5=>"apple", 4=>"kiwi", 6=>"carrot"}

In this example, the block takes each element of the array and returns an array with two elements: the length of the element and the element itself. The to_h method uses these returned arrays to create a hash, where the first element of each returned array becomes a key, and the second element becomes the corresponding value.

Practical Usage

The to_h method is useful when you want to create a hash from an array of data. You can also use it to convert an array of key-value pairs into a hash, which is often returned by methods like scan or zip. For more information, you can check the documentation here.

I hope this blog post helps you understand how to utilize the to_h method of Array in Ruby. Feel free to explore and experiment with this method in your own Ruby projects!

Banner photo by Donald Giannatti on Unsplash