class SystemData
	attr_reader :id

	def initialize(args = {})
		@backend = args[:backend]
		@id      = args[:id]
	end

	def save
    kind = self.class.to_s.to_sym

		if @id
			@backend.update(kind, to_h)
		else
			@backend.insert(kind, to_h)
		end
	end

	def to_h
		Hash[instance_variables.map do |var|
			[var[1...var.size].to_sym, eval(var)] if var != '@backend'
		end]
	end
end