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POHow do I set up to has_many/belongs_to assocations so that only one combination is allowed?
 

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  1. POHow do I set up to has_many/belongs_to assocations so that only one combination is allowed?
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    <p>I have three tables, applicants, users and ratings. The basic idea is that each applicant gets assigned a rating by any number of users. This part I have working without any problems. However, if a user goes to edit their rating (which includes a score), the form adds a second rating. I need to change things so that each user can only assign one rating for a given applicant.</p> <pre><code>class Applicant &lt; ActiveRecord::Base has_many :ratings accepts_nested_attributes_for :ratings, :allow_destroy =&gt; true class User &lt; ActiveRecord::Base has_many :ratings </code></pre> <p>The rating table just contains an applicant_id, a user_id and a score.</p> <pre><code>class Rating &lt; ActiveRecord::Base belongs_to :user belongs_to :applicant validates_uniqueness_of :applicant_id, :scope =&gt; :user_id </code></pre> <p>The rating validation makes sure that a second rating is not accepted, but I need to change the associations (or the form) so that a second score option never appears.</p> <p>My applicant form:</p> <pre><code>&lt;%= f.fields_for :ratings do |builder| %&gt; &lt;%= builder.collection_select :score, Rating::SCORES, :to_s, :humanize %&gt; &lt;%= builder.hidden_field :user_id, :value =&gt; current_user.id %&gt; &lt;%= builder.hidden_field :applicant_id, :value =&gt; @applicant.id %&gt; &lt;% end %&gt; </code></pre> <p>How do I specify (in the applicant model, I'd guess, since that's the form I'm editing) that the applicant_id, user_id combo in the ratings table has to be unique?</p>
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    1. USMary Heintz
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