rechash.rb

module ToHash
  def to_recursive_hash
    case self
      when Hash
        each_with_object({}) { |(k,v), h| h[k.to_sym] = v.to_recursive_hash }
      when Struct, OpenStruct
        to_h.each_with_object({}) { |(k,v), h| h[k.to_sym] = v.to_recursive_hash }
      when Array
        map(&:to_recursive_hash)
      else
        respond_to?(:to_h) ? to_h : self
    end
  end
end

OpenStruct.send(:include, ToHash)
Struct.send(:include, ToHash)
Hash.send(:include, ToHash)
Object.send(:include, ToHash)

rechash2.rb

module ToHash
  module_function def convert_recursively(value)
    case value
      when Hash
        value.each_with_object({}) { |(k,v), h| h[k.to_sym] = convert_recursively(v) }
      when Struct, OpenStruct
        value.to_h.each_with_object({}) { |(k,v), h| h[k.to_sym] = convert_recursively(v) }
      when Array
        value.map { |v| convert_recursively(v) }
      else
        value.respond_to?(:to_h) ? convert_recursively(value.to_h) : value
    end
  end
end