open_struct_example.rb

require "ostruct"

class User
  def initialize(basic_params)
    @json_params = OpenStruct.new(basic_params)
  end

  def full_name
    [
      @json_params.first_name,
      @json_params.last_name
    ].join(" ")
  end

  def method_missing(m)
    if @json_params.respond_to?(m)
      @json_params.send(m)
    else
      raise "Undefined method #{m}"
    end
  end
end

user_json = {
  first_name: "Foo", 
  last_name: "Bar"
}

user = User.new(user_json)
user.first_name
# => Foo

user.last_name
# => Bar

user.full_name
# => Foo Bar

user.blah
# => RuntimeError: Undefined method blah