Trouble splitting output of multiselect in Rails

Question

I have a multiselect (using bootstrap-multiselect) in my @minisets new form that aims to associate @scales with the @miniset via the @sizes table.

The associations work fine. What I'm stuck on is how to loop through the multiple :scale_id submissions from the multiselect and create lines in the @sizes table for them all.

Following this answer I have been trying to use split and then loop the create but I think the fact that that answer pertains to a HABTM relationship and mine is has_many_through means I need a different solution?

In my minisets controller I have

    def new
        @miniset = Miniset.new 
        @miniset.sizes.build
    end

    def create
        @miniset = Miniset.new(miniset_params)
        if @miniset.save
          params[:scale_id].split(',').each do |id|
            @miniset.sizes.create(params[:sizes_attributes])
        end
          redirect_to @miniset
        else
          render 'new'
        end
    end

private
    def miniset_params
      params.require(:miniset).permit(:name, :release_date, :material, :pcode, :notes, :quantity, :random, productions_attributes: [:id, :manufacturer_id, :miniset_id], sizes_attributes: [:id, :scale_id, :miniset_id], sculptings_attributes: [:id, :sculptor_id, :miniset_id])
    end
end

In my view I have

    <%= f.fields_for :sizes do |size_fields| %>
          <%= size_fields.label :scale_id, simple_pluralize(@miniset.scales.count, 'Scale') %>
         <%= size_fields.select :scale_id, 
                       options_from_collection_for_select(Scale.all, :id, :name, @miniset.scales.map(&:id)), 
                       {}, 
                       {class: 'multiselect', multiple: true} %>
    <% end %>

<script type="text/javascript">
      $(document).ready(function() {
        $('.multiselect').multiselect();
      });
    </script>

I'm currently getting error undefined methodsplit' for nil:NilClass` when I submit.

I think that may be because the log shows an empty scale_id passed before the two filled ones and split won't accept nil? Here is the log when submitting TWO scales.

Started POST "/minisets" for 127.0.0.1 at 2014-01-30 10:49:59 +0000
Processing by MinisetsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"R0RxDMwB5/ytSb5qgjIlVR5as0/DTkstgFMDXcefDnc=", "miniset"=>{"name"=>"Test for size", "quantity"=>"10", "random"=>"0", "material"=>"Hard Plastic", "sizes_attributes"=>{"0"=>{"scale_id"=>["", "1", "5"]}}, "pcode"=>"", "release_date(1i)"=>"", "release_date(2i)"=>"", "release_date(3i)"=>"", "notes"=>""}, "Set Scale"=>{"#<ActiveRecord::Associations::CollectionProxy::ActiveRecord_Associations_CollectionProxy_Size:0x007fcf643c29f0>"=>""}, "commit"=>"Add set"}
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."remember_token" = 'd59f28d384d62b71719dd845b4e5353cdd993016' LIMIT 1
Unpermitted parameters: scale_id
  SQL (0.9ms)  INSERT INTO "minisets" ("created_at", "material", "name", "notes", "pcode", "quantity", "updated_at") VALUES (?, ?, ?, ?, ?, ?, ?)  [["created_at", Thu, 30 Jan 2014 10:49:59 UTC +00:00], ["material", "Hard Plastic"], ["name", "Test For Size"], ["notes", ""], ["pcode", ""], ["quantity", 10], ["updated_at", Thu, 30 Jan 2014 10:49:59 UTC +00:00]]
  SQL (0.6ms)  INSERT INTO "sizes" ("created_at", "miniset_id", "updated_at") VALUES (?, ?, ?)  [["created_at", Thu, 30 Jan 2014 10:49:59 UTC +00:00], ["miniset_id", 41], ["updated_at", Thu, 30 Jan 2014 10:49:59 UTC +00:00]]
   (4.2ms)  commit transaction
Completed 500 Internal Server Error in 153ms

NoMethodError (undefined method `split' for nil:NilClass):
  app/controllers/minisets_controller.rb:19:in `create'

I'm sure what I have after the split is incorrect but I can't play with it until the split works. I can get rid of the error by adding to_s before the split but I get no better results.

Been making very slow progress on this multiselect for days now so any help very much appreciated.

Answer 1

Thanks to this fantastic youtube video I solved my problem.

My form:

<%= f.fields_for(@size) do |sf| %>
      <%= sf.label simple_pluralize(@miniset.scales.count, 'Scale') %>

        <%= collection_select( :scales, :id, @all_scales, :id, :name, 
                   {}, 
                   {class: 'multiselect', multiple: true}) %>
<% end %>

In my minisets_controller I have the following new and create actions:

def new
    @miniset = Miniset.new 
    @all_scales = Scale.all
    @size = @miniset.sizes.build
end

  def create
    @miniset = Miniset.new(miniset_params)
    params[:scales][:id].each do |scale|
      if !scale.empty?
        @miniset.sizes.build(:scale_id => scale)
      end
    end
    if @miniset.save
      redirect_to @miniset
    else
      render 'new'
    end
  end

It works perfectly. If anyone else is having the same problem, trying to get multiselects to work in rails with has_many_through, I recommend watching that video. So pleased.