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POActiveRecord and getting unused records from a relationship, find_by_sql or named_scope?
 

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  1. POActiveRecord and getting unused records from a relationship, find_by_sql or named_scope?
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    <p>Some context:</p> <p>I have some models that look like this</p> <p>Actor has_many Acts</p> <p>Act belongs_to Actor, belongs_to Decision</p> <p>Decision has_many Acts, belongs_to Prompt</p> <p>Prompt has_many Decisions</p> <p>What I need to do is in the ActorsController, get a random Prompt that has not been used yet of all the available Prompts.</p> <p>In my rails app, Actors are presented with prompts that give them a few choices to make. When they make a choice (Decision), that is saved in the db as an Act. </p> <p>I've tried various iterations of named_scope and find_by_sql, but none worked, and I'm not even sure if my thinking was right to begin with on them, since there are so many models at work, and I don't seem to know where to start.</p> <p>I hope this gives an idea of what I'm up against. I'd appreciate even a general pointer to form a plan of attack even.</p> <p>Thanks!</p> <p><em>edit</em></p> <p>After chewing on this for a couple hours, I've got something working but it's very messy, and my logs are filled with SQL calls, so it could definitely stand a critical eye.</p> <p>In the Prompt model:</p> <pre><code> named_scope :available, lambda { |used| { :conditions =&gt; ["id NOT IN (?)", used ] } } </code></pre> <p>In the Actor model:</p> <pre><code> def used_prompts prompts = Array.new if self.acts &amp;&amp; self.acts.length &gt;= 1 self.acts self.acts.each { |act| prompts.insert(0, act.decision.prompt.id) } return prompts.sort else return [0] end end </code></pre> <p>And in the ActorsController:</p> <pre><code>@prompt = Prompt.available(@actor.used_prompts).find(:first, :order =&gt; "RAND()") </code></pre> <p>Obviously the if block in used_prompts is one guilty party here, but I don't know a better way to deal with that since I can't do self.acts.decisions.each or some such thing. Maybe someone can school me :)</p>
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    1. USJohn
    1. USJohn
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    1. COusing RAND() will really really slow your queries down FYI.
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      1. POActiveRecord and getting unused records from a relationship, find_by_sql or named_scope?
      1. USPreston Marshall
 

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