Multiple instances of same model in form - parsing params hash - ruby-on-rails

Question

I'm admittedly a real novice at most of this, including forming and parsing params hashes. I'm trying to get a hash of instances of the same model from a form for a voting application. Users can vote for as many candidates as they wish according to rank.
My votes#new does create Candidate.count instances of Vote with the user_id and rank properly set. I know this because the form is correctly iterating through #user.votes for each candidate.
Here's a snippet of the rendered form:
<input id="vote_rank" name="vote[rank]" type="hidden" value="1" />
<label for="vote_Candidate">Candidate</label>
<select id="vote_candidate_id" name="vote[candidate_id]"><option value=""></option>
<option value="1">Smithers</option>
<option value="2">Mr. Burns</option>
<option value="3">Bart</option>
<option value="4">Lionel Hutz</option>
<option value="5">Jimbo</option>
<option value="6">Troy McClure</option>
<option value="7">Duffman</option>
<option value="8">Maggie</option>
<option value="9">Moe</option>
<option value="10">Principal Skinner</option>
<option value="11">Apu Nahasapeemapetilan</option></select>
I can't figure out how to get the collection back from the form to my votes#create. I am able to get a params hash with a single set of candidate_id and rank values (the last), but not all 11 instances I stuck in it in the first place. The form wants to give up the right data.
#user.votes.create(vote_params) in votes#create is throwing this error: undefined method `stringify_keys' for "rank":String
Here are my controller methods and form.
def new
#user = current_user
#votes = Candidate.count.times { |i| #user.votes.build(:rank => i + 1) }
end
def create
#user = current_user
#params[:user][:votes].each do |vote_params|
##user.votes.create(vote_params)
params[:vote].each do |vote_params|
#user.votes.create(vote_params)
end
respond_to do |format|
if #user.valid?
format.html { redirect_to #user, notice: 'votes were successfully created.' }
else
format.html { render action: "new" }
end
end
end
<%= form_for :votes, :url => votes_path do |f| %>
<% #user.votes.each do |v| %>
<%= fields_for v do |vote_fields| %>
<%= vote_fields.hidden_field :rank %>
<%= vote_fields.label "Candidate" %>
<%= vote_fields.collection_select :candidate_id, Candidate.all, :id, :name, :include_blank => true %>
<% end %>
<% end %>
<p><%= f.submit :class => 'medium radius button' %></p>
<% end %>
Here's the relevant HTML
Only one set of values is getting passed:
{"utf8"=>"✓", "authenticity_token"=>"bVLXCQtOffEtu5xBNI0e94o9j9mJ8alHhuBhDkkfaRA=", "vote"=>{"rank"=>"11", "candidate_id"=>""}, "commit"=>"Save Votes", "action"=>"create", "controller"=>"votes"}
although the form is trying to give up the right values:
vote[rank]:1
vote[candidate_id]:2
vote[rank]:2
vote[candidate_id]:4
vote[rank]:3
vote[candidate_id]:2
vote[rank]:4
vote[candidate_id]:9
etc. (up to 11!)
Any help appreciated.
Update:
Solved it sort of. I'm putting this up in case it helps someone since I haven't found anything directly on point and it took me a long time to figure this problem out.
My form was creating identically named objects, which were just overwriting. Explains why I was only ever able to get the last set of values into the database.
My form now iterates over the objects passed from votes#new and includes the vote's rank in the name.
<%= form_for :vote, :url => votes_path do |f| %>
<% #user.votes.each do |v| %>
<% if v.errors.any? %>
<h1>errors</h1>
<% end %>
<%= f.fields_for "#{v.rank}" do |builder| %>
<%= builder.hidden_field :rank, :value => v.rank %>
<div class="row">
<div class="one columns"><%= builder.label "Rank #{v.rank}", :class => "left inline" %></div>
<div class="eleven columns"><%= builder.collection_select :candidate_id, Candidate.all, :id, :name, {:include_blank => true}, :class => "two" %></div>
</div>
<% end %>
<% end %>
<%= f.submit "Submit", :confirm => "Please review your ballot and confirm that your votes are correct before submitting. This message will appear as a reminder each time you press 'Submit', even if you've edited your ballot.", :class => "small round button" %>
<% end %>
This craps out a params[:vote] hash of uniquely named hashes e.g.
{"1"=>{"rank"=>"1", "candidate_id"=>"5"}, "2"=>{"rank"=>"2", "candidate_id"=>"2"}, "3"=>{"rank"=>"3", "candidate_id"=>"7"}, "4"=>{"rank"=>"4", "candidate_id"=>"4"}, "5"=>{"rank"=>"5", "candidate_id"=>"10"}, "6"=>{"rank"=>"6", "candidate_id"=>""}, "7"=>{"rank"=>"7", "candidate_id"=>""}, "8"=>{"rank"=>"8", "candidate_id"=>""}, "9"=>{"rank"=>"9", "candidate_id"=>""}, "10"=>{"rank"=>"10", "candidate_id"=>""}, "11"=>{"rank"=>"11", "candidate_id"=>""}}
My votes#create method dumps an array made of key/value pairs from the params hash into #user.votes.create(my_array)
def create
#user = current_user
#user.votes.create(sanitize_and_compress_vote_array params[:vote])
redirect_to thankyou_path
end
Then next challenge is to get validation error messages to work properly. It's over my head because what I'm seeking to validate is an array of key value pairs by the uniqueness of candidate_id scoped by user_id before any values hit the database. It looks like Rails doesn't make this easy.
validates :candidate_id, :presence => true, :uniqueness => {:scope => :user_id, :message => "You may only vote for a candidate once."}
The validation works just fine for rejecting duplicate values, but it's useless because those values that already passed are obviously already in the database. I haven't found squat on how to validate members of a collection against themselves before they save and I feel like I'm talking to myself :-(