cannot visit enumerator edit_multiple
===

I am getting the following error when I try to edit multiple answers in my form and click save! 

    TypeError (Cannot visit Enumerator):
      app/controllers/answers_controller.rb:61:in `edit_multiple'

A User should be able to submit answers several times for the same study and the answers are saved as a study_instance that has the study_id, user_id, and the answers for the questions in that study. 
In the studies controller:

    def group_answers
    @study = Study.find_by_slug(params[:id])
    @study_instance = StudyInstance.find(params[:study_instance])
    @answers = @study_instance.answers
    respond_to do |format|
      format.html 
      format.json { render :json => @study }
    end
    end
 
In the answers controller I have this:

    def edit_multiple
      @keys = params[:answer].keys.collect
      @answers = Answer.where(:id => @keys)
      @answers.each { |t| t.attributes = params[:answer][t.id.to_s] }
      if @answers.all?(&:valid?)
        @answers.each(&:save!)
        redirect_to studies_url, :notice => 'Study was successfully changed.'
      else
        return
      end
    end

And in the group_answers view: 

    .block
      .content
        .inner
          %h2
            = @study.title
          %p.description
            = @study.description
            = @questions
    = form_for :answers, :url => edit_multiple_answers_path, :html => { :multipart => true }     do |f|
      - @study_instance.answers.by_position.each do |answer|
        .block
          .content
            .inner
              %p
                = answer.position
                \.
                = answer.question.question_text
                %br/
                = fields_for "answer[#{answer.id}]" do |f|
                  - if answer.question.long_text
                    = f.text_area :answer_text, :value => answer.answer_text
                  - elsif answer.question.short_text
                    = f.text_field :answer_text, :value => answer.answer_text
                  - elsif answer.question.file_upload
                    = f.file_field :answer_image
                    %br/
                    %span.description 
                      Must be at least 500px x 500px and in gif or jpg format. 
                      %br/
                      No characters other than letters and numbers in file name.
                      %br/
                      Current_file:
                      %br/
                      = answer.answer_image_file_name ? (image_tag     answer.answer_image.url(:thumb)) : "none"
                  - else
                    = f.select :answer_text, answer.question.options_from_choices, :selected     => answer.answer_text, :include_blank => true

      .group.navform.wat-cf
        %button.button{:type => "submit"}
          = image_tag("web-app-theme/icons/tick.png", :alt => "#{t("web-app-theme.save",     :default => "Save")}")
          = t("web-app-theme.save", :default => "Save")
        %span.text_button_padding= t("web-app-theme.or", :default => "or")
        = link_to t("web-app-theme.cancel", :default => "Cancel"), studies_path, :class =>     "text_button_padding link_button"

I am still new to rails and apoligize if this is something very simple but it has stumped me.  