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Ruby on Rails - maximum number of related objects?

I need help with a request. I have many eateries where everyone has several dishes, where each meal has several MealPicks.

Although I don’t know if this MealPick model MealPick good idea, because I need to display how many times the food was selected TODAY, so I need a timestamp to make this request.

 class Meal < ActiveRecord::Base def todays_picks meal_picks.where(["created_at >= ? AND created_at < ?", Date.today.beginning_of_day, Date.today.end_of_day]) end end

Before I only had the meal_picked_count counter in Meal, which I incremented with the increment_counter method.

So, now I need to display for each dining room, in which MealPicks is the most , I played in the console and tried something like Canteen.find(1).meals.maximum("meal_picks.count") , but this obviously does not work. not a column.

Any ideas?

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 canteen.meals.max {|m| m.meal_picked_count}
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You can do it:

 MealPick.joins(:meal => :canteen) .where("canteens.id = ?", 1) .order("count_all DESC") .group(:meal_id) .count

This will return an ordered hash as follows:

 { 200 => 25 }

Where 200 will be the identifier of the food, and 25 will be the counter.

Update

For everyone who is interested, I started playing with this to find out if I can use subqueries with ActiveRecord to give me meaningful information than before. Here is what I have:

 class Meal < ActiveRecord::Base belongs_to :canteen has_many :meal_picks attr_accessible :name, :price scope :with_grouped_picks, ->() { query = <<-QUERY INNER JOIN (#{Arel.sql(MealPick.counted_by_meal.to_sql)}) as top_picks ON meals.id = top_picks.meal_id QUERY joins(query) } scope :top_picks, with_grouped_picks.order("top_picks.number_of_picks DESC") scope :top_pick, top_picks.limit(1) end class MealPick < ActiveRecord::Base belongs_to :meal attr_accessible :user scope :counted_by_meal, group(:meal_id).select("meal_id, count(*) as number_of_picks") scope :top_picks, counted_by_meal.order("number_of_picks DESC") scope :top_pick, counted_by_meal.order("number_of_picks DESC").limit(1) end class Canteen < ActiveRecord::Base attr_accessible :name has_many :meals has_many :meal_picks, through: :meals def top_picks @top_picks ||= meals.top_picks end def top_pick @top_pick ||= top_picks.first end end

This allows me to do this:

 c = Canteen.first c.top_picks #Returns their meals ordered by the number of picks c.top_pick #Returns the one with the top number of picks

Let's say that I wanted to order all the dishes according to the number of peaks. I could do this:

 Meal.includes(:canteen).top_picks #Returns all meals for all canteens ordered by number of picks. Meal.includes(:canteen).where("canteens.id = ?", some_id).top_picks #Top picks for a particular canteen Meal.includes(:canteen).where("canteens.location = ?", some_location) #Return top picks for a canteens in a given location

Since we use union, grouping, and server-side counts, the entire collection does not need to be loaded to determine the sampling counter. It is a little more flexible and probably more efficient.

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