# Ruby: Immutable Value Object with Struct

Freezing the initializer after passing the args to `super` makes the object immutable.

```rb
# frozen_string_literal: true

# Freezing the initializer after passing the args to `super` makes the object immutable.
#
# Example:
#
#   require 'value_object'
#
#   ForcePullData = Struct.new(:repository_name, :site_id, keyword_init: true) do
#     include ValueObject
#   end
#
#   data = ForcePullData.new(repository_name: 'sandbox', site_id: 'site-id')
#
#   > data.repository_name
#   => "sandbox"
#
#   > data.repository_name = "plaything"
#   FrozenError: can't modify frozen ForcePullData:
#   #<struct ForcePullData repository_name="sandbox", site_id="site-id">
module ValueObject
  def initialize(**args)
    super(args)
    freeze
  end
end
```

This trick comes from [Polished Ruby Programming](https://www.amazon.com/Polished-Ruby-Programming-maintainable-high-performance-ebook/dp/B093TH9P7C) by [Jeremy Evans](https://github.com/jeremyevans).