Trouble splitting output of multiselect in Rails - ruby-on-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.