Question

我在研究一个简单的项目在那里我有两个样本参考模型:

class Player
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :games
end

class Game
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :players
end

我需要做的是获得一个与玩家数组玩过的顶级游戏列表。类似地 :

{
  "diablo_3": {
    "players": 89
  },
  "max_payne_3": {
    "players": 87
  },
  "world_of_warcraft": {
    "players": 65
  },
  "dirt_3": {
    "players": 43
  }
}

谢谢谢谢

Answer 1

You can use the MongoDB group command to do some server-size processing on a single collection, and it is available as a method on the collection in the Ruby driver, see http://api.mongodb.org/ruby/current/Mongo/Collection.html#group-instance_method

Below please find a test based on your models, with the title field added to your Game model. This is a working answer to your question that uses MongoDB s group command.

require  test_helper 

class GameTest < ActiveSupport::TestCase
  def setup
    Player.delete_all
    Game.delete_all
  end

  test "game player count" do
    input = [ [  diablo_3 , 89 ], [  max_payne_3 , 87 ], [  world_of_warcraft , 65 ], [  dirt_3 , 43 ] ]
    input.shuffle.each do | title, count |
      game = Game.create(title: title)
      (0...count).each{ game.players << Player.new }
    end
    game_player_count = Game.collection.group(key: :_id, cond: {}, initial: {count: 0}, reduce:  function(doc, out) { out.title = doc.title; out.count = doc.player_ids.length; } )
    game_player_count.sort!{|a,b| -(a[ count ] <=> b[ count ]) }
    game_player_count = Hash[*game_player_count.map{|r| [r[ title ], {"players" => r[ count ].to_i} ]}.flatten]
    puts JSON.pretty_generate(game_player_count)
  end

end

结果结果结果结果结果

Run options: --name=test_game_player_count

# Running tests:

{
  "diablo_3": {
    "players": 89
  },
  "max_payne_3": {
    "players": 87
  },
  "world_of_warcraft": {
    "players": 65
  },
  "dirt_3": {
    "players": 43
  }
}
.

Finished tests in 0.482286s, 2.0735 tests/s, 0.0000 assertions/s.

1 tests, 0 assertions, 0 failures, 0 errors, 0 skips

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