Challenge 3: A Minimal OpenStruct — Solution

class DynamicRecord
  def initialize(attributes)
    @attributes = attributes
  end

  def method_missing(method_name, *args)
    if @attributes.key?(method_name)
      @attributes[method_name]
    else
      super
    end
  end

  def respond_to_missing?(method_name, include_private = false)
    @attributes.key?(method_name) || super
  end
end

record = DynamicRecord.new(name: "Philip", role: "Student")

puts record.name
puts record.role
puts record.respond_to?(:name)
puts record.respond_to?(:nonexistent_field)

=begin
Output:
Philip
Student
true
false

Notes:
- method_missing checks whether the called method's name matches a key in
  @attributes; if so, it returns that value instead of raising
  NoMethodError. Calling super in the else branch preserves normal Ruby
  behavior for any genuinely unhandled method name.
- respond_to_missing? mirrors the exact same check, which is why
  record.respond_to?(:name) correctly returns true even though name was
  never defined with def anywhere in the class.
- record.respond_to?(:nonexistent_field) correctly returns false, proving
  respond_to_missing? and method_missing agree with each other — the
  chapter's warning about skipping respond_to_missing? would show up here
  as a mismatch between what respond_to? reports and what actually happens
  when the method is called.
=end