title: Rails Form Helper not reading question mark for object attribute
body: <p><strong>Ruby Version: 2.0</strong></p>
  
  <p><strong>Rails Version: 4.0</strong></p>
  
  <p>I have a controller <code>Question</code>, which has an embedded form for a model <code>Answer</code>.</p>
  
  <p><strong>question.rb</strong></p>
  
  <pre><code>class Question &lt; ActiveRecord::Base
      has_many :answers, :dependent =&gt; :destroy
      accepts_nested_attributes_for :answers, :allow_destroy =&gt; true
  end
  </code></pre>
  
  <p><strong>answer.rb</strong></p>
  
  <pre><code>class Answer &lt; ActiveRecord::Base
      belongs_to :question
  end
  </code></pre>
  
  <p><strong>answers migration</strong></p>
  
  <pre><code>class CreateAnswers &lt; ActiveRecord::Migration
    def change
      create_table :answers do |t|
        t.string :text
        t.integer :question_id
        t.boolean :correct?
  
        t.timestamps
      end
    end
  end
  </code></pre>
  
  <p>in the form, when editing or creating a new question - the user may enter up to 4 possible answers, and mark a check box for the "correct" answer(s).</p>
  
  <p><strong>/views/questions/_form.html.erb</strong></p>
  
  <pre><code>&lt;%= form_for(@question) do |f| %&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :text %&gt;&lt;br&gt;
      &lt;%= f.text_area :text %&gt;
    &lt;/div&gt;
  
    &lt;p&gt;Enter up to 4 posisble answer choices.&lt;/p&gt;
    &lt;%= f.fields_for :answers do |answer| %&gt;
      &lt;div class="field"&gt;
        &lt;%= answer.text_field :text %&gt;
        &lt;%= answer.check_box :correct? %&gt;
      &lt;/div&gt;
    &lt;% end %&gt;
  
    &lt;div class="actions"&gt;
      &lt;%= f.submit %&gt;
    &lt;/div&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p><strong>relevant snippets from questions_controller.rb</strong></p>
  
  <pre><code>def new
      @question = Question.new
      4.times { @question.answers.build }
    end
  
  private
      # Use callbacks to share common setup or constraints between actions.
      def set_question
        @question = Question.find(params[:id])
      end
  
      # Never trust parameters from the scary internet, only allow the white list through.
      def question_params
        params.require(:question).permit(:text, :quiz_id, answers_attributes: [:id, :text, :correct?])
      end
  </code></pre>
  
  <p><strong>Finally - on to my problem</strong></p>
  
  <p>Everything listed above worked perfectly until I added the checkboxes for <code>answer.correct?</code>. When I submit the form as is I get this message in my logs:</p>
  
  <pre><code>Unpermitted parameters: correct
  Unpermitted parameters: correct
  Unpermitted parameters: correct
  Unpermitted parameters: correct
  </code></pre>
  
  <p>Weird... there is definitely a question mark at the end of that parameter. Allowing this to pass through without the question mark be editing the allowed parameters in the controller gets me this error message:</p>
  
  <p><code>unknown attribute: correct</code> (this one actually throws an error message, I don't have to go digging in the logs to find this.)</p>
  
  <p><strong>How do I get the form helper to read the question mark?</strong></p>