return instance through nested iteration

Question

For customer_favs I was able to save all the instances of a favorite for the current customer I am working with. The favorite for a customer consists of the customer id and restaurant id. With that I decided to iterate through it and also iterate through all of the restaurants and see if the id of that the restaurant instance is the same as the restaurant_id of the favorite and return it which gives me an array of favorites.

Now what I am trying to do is find a way to return the instance of the restaurant through the favorite which contains the restaurant_id, I just want to get the restaurant's name. I decided to iterate again though the array of favorites and iterate through the restaurants and compare to see if the restaurant_id of the favorites is the same as the one of the instances of the restaurant and have those instances saved inside of the variable but I am getting an error saying " undefined method `restaurant_id' ".

def view_all_favorites(customer)
  customer_favs = customer.favorites

  get_res_id = customer_favs.each do |fav_res|
    Restaurant.all.select do |res|
      res.id == fav_res.restaurant_id
    end
  end

  get_res = Restaurant.all.select do |res|
    get_res_id.restaurant_id == res.id
  end

  puts "#{get_res}"
end

`each` always returns the object being iterated. That's not what you want here. Additionally `Restaurant.all` fetches *every* restaurant in the database regardless of if it matches or not and is really inefficient. Try and use `where` queries. — tadman, Oct 19 '19 at 00:14
It's hard to tell what's going on here but you may be over-complicating things. What you probably want is `customer.favorites.restaurants` if `Favorite` has a `belongs_to :restaurant` and `Customer` has a `has_many :restaurants, through: :favorites`. — tadman, Oct 19 '19 at 00:16
@tadman, I tried doing so and I got an error saying undefined method `restaurants' — hannah, Oct 19 '19 at 00:58
Make sure you did `has_many :restaurants` and not `has_many restaurants` as the missing colon makes it appear to be a method call. — tadman, Oct 21 '19 at 19:19

Luke Persola · Accepted Answer · 2019-10-19T01:27:59.780

The problems mentioned in the comments are significant, but here's a light edit to get it working:

def view_all_favorites(customer)
  customer_favs = customer.favorites # get favorites from customer

  get_res_id = customer_favs.map do |fav_res| # get restaurant IDs from favorites
    fav_res.restaurant_id
  end

  get_res = Restaurant.all.select do |res| # get restaurants from their IDs
    get_res_id.include?(res.id)
  end

  res_names = get_res.map do |res| # get names from restaurants
    res.name
  end

  puts "#{res_names}"
end

That could probably be simplified to something like this:

def view_all_favorites(customer)
  favorite_restaurants = Restaurant.where(id: customer.favorites.map(&:restaurant_id))
  puts favorite_restaurants.map(&:name)
end

But, as tadman said, it's preferable to set up relations so you don't even have to do that.

and for the second code can you explain to me what the & is for? — hannah, Oct 19 '19 at 02:00
`restaurants.map(&:name)` is the same as `restaurants.map{ |r| r.name }`. For more details see: https://stackoverflow.com/questions/9429819/what-is-the-functionality-of-operator-in-ruby — Luke Persola, Oct 19 '19 at 02:07

return instance through nested iteration

1 Answers1