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    <p>There's many different ways to do this, but i tend to think that <strong>you have a design problem</strong> here, so here's how i would do it. </p> <p>I assume from what you said that your associations look like this :</p> <pre><code> __________ ________ | Question |1 *| Answer | | |&lt;-------------------------------| | | |1 * ___________ * 1| | | |&lt;------| Selection |-----------&gt;|________| | | | | | | | |* 1 ________ | | |___________|-----------&gt;| User | | |* 1| | |__________|-------------------------------&gt;|________| </code></pre> <p>This visual representation clearly shows the problem : your <code>Selection</code> model is redundant, as it represents the fact that a question <code>belongs_to</code> a <code>User</code> (which we already know) ; it would not be redundant if there could be multiple selections for each couple of <code>Question / User</code>, but in practice we <strong>want</strong> that selection to be unique for each couple...</p> <p>A <code>belongs_to</code> relation between <code>Question</code> and <code>Answer</code> would achieve the same thing that your <code>Selection</code> model does, and in fact <em>it would do it better</em> because you won't need all the logic to find the right selection, and to ensure it is unique / that the user is the rightfull owner of the question, etc.</p> <p>So here's what i'd do :</p> <ul> <li><p>In the <code>Question</code> model</p> <pre><code>has_many :answers, inverse_of: :question belongs_to :accepted_answer, class_name: :answer, foreign_key: :accepted_answer_id </code></pre></li> <li><p>In the <code>Answer</code> model</p> <pre><code>belongs_to :question, inverse_of: :answers def accepted? return false if new_record? question.try( :accepted_answer_id ) == id # an alternative is to use question.try( :accepted_answer ) == self end </code></pre></li> <li><p>In your routes</p> <pre><code>resources :questions do member do # we use put because these are update actions put :accept_answer put :clear_accepted_answer end end </code></pre></li> <li><p>In your <code>QuestionsController</code></p> <pre><code>respond_to :js, only: [:accept_answer, :clear_accepted_answer] def accept_answer @question = Question.find( params[:id] ) # ...cue some logic to ensure current_user # has required rights to update the question if @question.update_attributes( accepted_answer_id: params[:answer_id] ) # ...render the js that updates your view (for example, # find and replace calling link with an "unselect" one ) else # .. an error has occurred, render an "unprocessable entity" status end end def clear_accepted_answer @question = Question.find( params[:id] ) # ...cue some logic to ensure current_user # has required rights to update the question if @question.update_attributes( accepted_answer_id: nil ) # ...render the js that updates your view (for example, # find and replace calling link with a "select" one ) else # .. an error has occurred, render an "unprocessable entity" status end end </code></pre></li> <li><p>in your view</p> <pre><code> &lt;% if current_user?(answer.question.user) %&gt; &lt;% if answer.accepted? %&gt; &lt;%= link_to "unselect", clear_accepted_answer_question_path( answer.question ), method: :put, remote: true %&gt; &lt;% else %&gt; &lt;%= link_to "select", accept_answer_question_path( answer.question, answer_id: answer.id ), method: :put, remote: true %&gt; &lt;% end %&gt; &lt;% end %&gt; </code></pre></li> </ul>
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    1. COThanks for your very well thought-out and crafted answer...I truly appreciate it. I will certainly look to learn more about model relationships (I'm just seeing `inverse_of` for the first time now), and then update both my code as well as evaluate my other models to to see if they could benefit from better design. Thanks again.
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    2. COyou're welcome. For the record, `inverse_of` here is not absolutely necessary, but i tend to use it everywhere because (as i understand it) it prevents ActiveRecord from reloading an association when you do something like `question.answers.first.question` (where question would be reloaded save for the inverse_of)
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    3. COIt appears that `question.accepted_answer_id` isn't getting recognized (I get the "undefined method" error). Changing it from `_id` to `.id` also resulted in an error, although it was "Called id for nil". I ensured that my `Question.rb` had the line `belongs_to :accepted_answer, class_name: :answer`, so I don't know why `accepted_answer` was not getting recognized when called from the view via `if answer.accepted?`. Thanks for the help again.
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