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PORails 3 - How can you sort an AR query result by doing math on attributes?
 

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  1. PORails 3 - How can you sort an AR query result by doing math on attributes?
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    <p>I'm building a controller/view that provides a wide selection of player rankings (e.g. "Top 10 Leader Boards".) Using this model:</p> <pre><code>class Player &lt; ActiveRecord::Base attr_accessible :name, :games_played, :games_lost, :games_won, games_exited, :total_kills, :total_deaths, :total_points, :total_coins end </code></pre> <p>In my controller I have some obvious query results to pass to my view to populate player ranking lists:</p> <pre><code>@top_winners = Player.order("games_won DESC").limit(10) @top_assassins = Player.order("total_kills DESC").limit(10) </code></pre> <p>I now need to add some sorted rankings that are calculations. Examples:</p> <pre><code>@most_greedy would be sorted on: :total_coins / :games_played @most_lethal would be sorted on: :total_kills / :games_played @most_vanquished would be sorted on: :total_deaths / (:games_lost + :games_exited) </code></pre> <p>My approach is to get all the players in an array and then use Ruby's <code>array.sort {| a,b | block } → new_array</code> option. In the case of <code>@most_greedy</code> I tried this:</p> <pre><code>rich_players = Player.order("total_coins DESC").limit(30) # only consider top 30 richest @most_greedy = rich_players.sort {|total_coins, games_played| x / y }.slice(0, 9) </code></pre> <p>Which generates the error:</p> <pre><code>undefined local variable or method `x' for #&lt;PlayersController:0x007fb7dac59d08&gt; </code></pre> <p>Unfortunately my meager AR understanding and Ruby skills are failing me. How can I make this approach work? Is there a different approach to this type of problem? I didn't see anything in the AR Query Guide like this.</p>
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    1. USDon Leatham
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