ActiveRecord Practice Exercises

Overview

In this lab, you'll practice all of the parts of ActiveRecord - Migrations, Validations, Seeds, and Querying.

Introduction

We'll be building out a restaurant domain in two stages. Remember to draw out the relationships between your models before you start building.

Stage 1

We'll be creating the following models:

• Restaurant
• Dish
• Tag

Migrations

• Restaurant
  • name
  • has many dishes
• Dish
  • name
  • has many tags
• Tag
  • name
  • has many dishes

Do you need any join tables? What data should they have?

Validations

• Restaurants need a name
• Dishes need a name and a restaurant
• Tags need a name 3 characters or longer
• Tag names can only be one word or two words, not more
• Dishes can only have one of any particular tag

Seeds

Create a seeds file that creates:

• 20 restaurants.
• Each restaurant should have 10 dishes
• Each Dish should have 3 tags
• There should be only 10 or 15 tags, with names like 'Spicy' and 'Vegetarian'

Reminder: Be DRY - use an array of names and iterate through them to create your restaurants

Querying

Write the following methods. You should use ActiveRecord query methods to get the results (i.e. you shouldn't just use .all and use array methods!)

Note: some helper methods you will need (e.g. the relationships between the models) are not listed here. Write them anyway!

Restaurant

• Restaurant.mcdonalds - find the restaurant with the name 'McDonalds'.
• Restaurant.tenth - find the tenth restaurant
• Restaurant.with_long_names - find all the restaurants with names longer than 12 characters
• Restaurant.max_dishes - find the restaurant with the most dishes
• Restaurant.focused - find all the restaurants with fewer than 5 dishes
• Restaurant.large_menu - find all the restaurants with more than 20 dishes
• Restaurant.vegetarian - all restaurants where all of the dishes are tagged vegetarian
• Restaurant.name_like(name) - all restaurants where the name is like the name passed in
• Restaurant.name_not_like(name) - all restaurants where the name is not like the name passed in

Dish

• Dish.names - all the names of dishes
• Dish.max_tags - single dish with the most tags
• Dish.untagged - dishes with no tags
• Dish.average_tag_count - average tag count for dishes
• Dish#tag_count - number of tags for a dish
• Dish#tag_names - names of the tags on a dish
• Dish#most_popular_tag - most widely used tag for a dish

Tag

• Tag.most_common - tag with the most associated dishes
• Tag.least_common - tag with the fewest associated dishes
• Tag.unused - all tags that haven't been used
• Tag.uncommon - all tags that have been used fewer than 5 times
• Tag.popular - top 5 tags by use
• Tag#restaurants - restaurants that have this tag on at least one dish
• Tag#top_restaurant - restaurant that uses this tag the most
• Tag#dish_count - how many dishes use this tag

ActiveRecord methods you might find useful:

• find
• where
• pluck
• joins
• includes
• group
• having

Examples and explanations here

Note: In order to test these methods, you'll probably need to have particular seed data. Create it.

Stage 2

Mo models, mo problems.

Add the following models to the domain:

• Customer
• Order
• Review

Migrations

• Customer
  • name
  • lat
  • lon
  • has many orders
  • has many reviews
• Order
  • belongs to a customer
  • belongs to a restaurant
  • has many dishes
• Review
  • content
  • rating
  • date
  • belongs to a customer
  • belongs to a restaurant

And add to your old models

• Dish
  • price
  • cost (price the restaurant paid to make it)
• Restaurant
  • lat
  • lon

Again - what other tables do you need? Draw your relationships to find out.

Validations

• Customer name is required
• Customer lat and lon must be valid latitude and longitude (-90 < lat < 90, -180 < lon < 180)
• Order needs a customer and a restaurant
• Order needs at least one dish
• Order dishes must all be from the same restaurant
• Review must have a customer and a restaurant
• Review must have content > 10 characters
• Review rating must exist, be one of the values [1,2,3,4,5]. See Enums.
• Review customer must have made an order from the restaurant

Queries You'll need to update your old seed data and add more to be able to test these query methods.

Customer

• Customer#recent_reviews - all reviews by this customer, ordered by recency
• Customer#nearest_restaurant - nearest restaurant to the customer's location
• Customer#top_restaurant - restaurant where the customer has the most orders
• Customer#top_dish - most commonly ordered dish for the customer
• Customer#total_spending - total price of all dishes ordered
• Customer.top_spenders - top 5 customers by total order price

Order

• Order#total_price - sum of the price of all the dishes.
• Order#profit - difference between price and cost of all the order's dishes
• Order#profitable? - true if order profit is positive
• Order#tags - tags of all the dishes in an order
• Order.cheapest - lowest 5 orders by total price
• Order.most_expensive - highest 5 orders by total price

Review

• Review.median_rating - median rating for all reviews
• Review.most_recent - most recent 10 reviews

Restaurant

• Restaurant#average_rating - average rating of a restaurant
• Restaurant.average_rating - average rating across all restaurants
• Restaurant.highest_rated - highest average rated restaurant
• Restaurant.top_five - top five highest rated restaurants
• Restaurant#dollar_rating - how many dollar signs is this restaurant?
  • $: avg_dish_price < 10
  • $$: 10 < avg_dish_price < 20
  • $$$: 20 < avg_dish_price < 30
  • $$$$: 30 < avg_dish_price
• Restaurant.most_expensive - most expensive restaurant by average dish price
• Restaurant.cheap_eats - all $ and $$ restaurants
• Restaurant.nearest_customers - nearest 5 customers
• Restaurant.recent_reviews - 5 most recent reviews of this restaurant
• Restaurant#best_seller - most ordered dish for the restaurant
• Restaurant#most_profitable_dish - most profitable dish (price - cost) * num orders

Dish

• Dish#top_customer - customer who has ordered a dish the most times
• Dish.most_ordered - most ordered dish

Tag

• Tag#nearest_restaurant(customer) - nearest restaurant to the customer with that tag.
• Tag#top_rated - top 3 rated restaurants with dishes with a tag

Bonus 1. Schema Constraints

Read this about schema constraints. Add the appropriate schema constraints to your tables. For instance, things that have a validation for presence: true should probably also have null: false in the schema.

Bonus 2. N+1 Queries

Read the section of the rails guide about N+1 queries and Eager Loading Associations. Using the ActiveRecord Logger, find out which of the methods you've written so far have an N+1 query. Fix them.