Rails 3 - 如何从具有订单的模型中获取行号

Question

我正在整理一个具有排行榜概念的小应用程序.基本上,模型只是一个player_name和一个current_score.

我想要做的是获得特定玩家的排名,并且考虑到新的分数一直在进行,它需要是动态的.显然,我可以使用order by子句进行正常查找,然后我必须循环遍历每条记录.当我有100,000行时,效率不高.

我应该采取什么方法的任何建议？

以下是表的迁移:

class CreateScores < ActiveRecord::Migration
  def self.up
    create_table :scores do |t|
      t.string  :player_name
      t.integer :current_score

      t.timestamps
    end
  end

  def self.down
    drop_table :scores
  end
end

编辑作为一个例子,所以我有以下内容:

Score.select('player_name, current_score').limit(20)
=> [#<Score player_name: "Keith Hughes", current_score: 9>, #<Score player_name: "Diane Chapman", current_score: 8>, #<Score player_name: "Helen Dixon", current_score: 4>, #<Score player_name: "Donald Lynch", current_score: 9>, #<Score player_name: "Shawn Snyder", current_score: 2>, #<Score player_name: "Nancy Palmer", current_score: 9>, #<Score player_name: "Janet Arnold", current_score: 1>, #<Score player_name: "Sharon Torres", current_score: 9>, #<Score player_name: "Keith Ortiz", current_score: 5>, #<Score player_name: "Judith Day", current_score: 3>, #<Score player_name: "Gregory Watson", current_score: 7>, #<Score player_name: "Jeremy Welch", current_score: 3>, #<Score player_name: "Sharon Oliver", current_score: 7>, #<Score player_name: "Donald Lewis", current_score: 7>, #<Score player_name: "Timothy Frazier", current_score: 7>, #<Score player_name: "John Richards", current_score: 1>, #<Score player_name: "Carolyn White", current_score: 4>, #<Score player_name: "Ronald Smith", current_score: 2>, #<Score player_name: "Emily Freeman", current_score: 9>, #<Score player_name: "Gregory Wright", current_score: 2>]

我如何计算出"唐纳德刘易斯"的排名？

Answer 1

您可以计算具有更高current_score的记录数.您仍然必须按记录执行此操作(或在您的sql中执行子查询).

class Score < ActiveRecord::Base

  def ranking
    Score.count(:conditions => ['current_score > ?', self.current_score])
  end

end