Module: ArchSpec::ValueObject

Defined in:
lib/archspec/value_object.rb

Overview

A frozen value type with positional or keyword construction and #with, mirroring Ruby 3.2's Data.define. Deliberately hand-rolled: the gem supports Ruby 3.1, where Data does not exist. Do not replace this with Data until the required Ruby version reaches 3.2.

Class Method Summary collapse

Class Method Details

.define(*members, &block) ⇒ Object 



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# File 'lib/archspec/value_object.rb', line 9

def self.define(*members, &block)
  klass = Struct.new(*members) do
    members.each { |member| undef_method :"#{member}=" }

    def initialize(*values, **keywords)
      member_names = self.class.members

      if keywords.any?
        raise ArgumentError, 'expected positional arguments or keyword arguments, not both' unless values.empty?

        unknown = keywords.keys - member_names
        raise ArgumentError, "unknown keyword: #{unknown.first.inspect}" if unknown.any?

        missing = member_names - keywords.keys
        raise ArgumentError, "missing keyword: #{missing.first.inspect}" if missing.any?

        values = member_names.map { |member| keywords.fetch(member) }
      elsif values.length != member_names.length
        raise ArgumentError, "wrong number of arguments (given #{values.length}, expected #{member_names.length})"
      end

      super(*values)
      freeze
    end

    def with(**changes)
      unknown = changes.keys - self.class.members
      raise ArgumentError, "unknown keyword: #{unknown.first.inspect}" if unknown.any?

      self.class.new(**to_h.merge(changes))
    end
  end

  klass.class_eval(&block) if block
  klass
end