How to change the default value of a Struct attribute?

Question

According to the documentation unset attributes of Struct are set to nil:

unset parameters default to nil.

Is it po

Answer 1

I think that the override of the #initialize method is the best way, with call to #super(*required_args).

This has an additional advantage of being able to use hash-style arguments. Please see the following complete and compiling example:

Hash-Style Arguments, Default Values, and Ruby Struct

# This example demonstrates how to create Ruby Structs that use
# newer hash-style parameters, as well as the default values for
# some of the parameters, without loosing the benefits of struct's
# implementation of #eql? #hash, #to_s, #inspect, and other
# useful instance methods.
#
# Run this file as follows
#
# > gem install rspec
# > rspec struct_optional_arguments.rb --format documentation
#
class StructWithOptionals < Struct.new(
    :encrypted_data,
    :cipher_name,
    :iv,
    :salt,
    :version
    )

    VERSION = '1.0.1'

    def initialize(
        encrypted_data:,
        cipher_name:,
        iv: nil,
        salt: 'salty',
        version: VERSION
        )
        super(encrypted_data, cipher_name, iv, salt, version)
    end
end

require 'rspec'
RSpec.describe StructWithOptionals do
    let(:struct) { StructWithOptionals.new(encrypted_data: 'data', cipher_name: 'AES-256-CBC', iv: 'intravenous') }

    it 'should be initialized with default values' do
        expect(struct.version).to be(StructWithOptionals::VERSION)
    end

    context 'all fields must be not null' do
        %i(encrypted_data cipher_name salt iv version).each do |field|
            subject { struct.send(field) }
            it field do
                expect(subject).to_not be_nil
            end
        end
    end
end