customer_repository.rb

require 'csv'
require_relative '../models/customer'

class CustomerRepository
	def initialize(csv_path)
		@csv_path = csv_path
		@customers = []
		load_csv if File.exist?(@csv_path)
		@next_id = @customers.empty? ? 1 : @customers.last.id + 1
	end

	def all
		@customers
	end

	def add(customer)
		customer.id = @next_id
		@customers << customer
		save_csv
		@next_id += 1
	end

	private

	def load_csv
		options = { headers: :first_row, header_converters: :symbol }
		CSV.foreach(@csv_path, options) do |row|
			row[:id] = row[:id].to_i
			@customers << Customer.new(row)
		end
	end

	def save_csv
		CSV.open(@csv_path, "wb") do |csv|
			csv << ["id", "name", "address"]

			@customers.each do |customer|
				csv << [customer.id, customer.name, customer.address]
			end
		end
	end
end

meal_repository.rb

require 'csv'
require_relative '../models/meal'

class MealRepository
	def initialize(csv_path)
		@csv_path = csv_path
		@meals = []
		load_csv if File.exist?(@csv_path)
		@next_id = @meals.empty? ? 1 : @meals.last.id + 1
	end

	def all
		@meals
	end

	def add(meal)
		meal.id = @next_id
		@meals << meal
		save_csv
		@next_id += 1
	end

	private

	def load_csv
		options = { headers: :first_row, header_converters: :symbol }
		CSV.foreach(@csv_path, options) do |row|
			row[:id] = row[:id].to_i
			row[:price] = row[:price].to_i
			@meals << Meal.new(row)
		end
	end

	def save_csv
		CSV.open(@csv_path, "wb") do |csv|
			csv << ["id", "name", "price"]

			@meals.each do |meal|
				csv << [meal.id, meal.name, meal.price]
			end
		end
	end
end