I am trying to get a collection select from an another model and I keep getting the above error. Looked everywhere, got rails casts but nothing makes sense.

_form.rb

 <%= f.label :city %><br />
 <%= f.collection_select (:share ,:city_id, City.all , :id, :name ) %>

It highlights 'form' on the error report

<h1>New share</h1>
<%= render 'form' %>
<%= link_to 'Back', shares_path %>

Here are my models...

class Share
  include Mongoid::Document
  field :name, type: String
  field :type, type: String
  field :summary, type: String
  field :description, type: String
  field :city, type: String

  embedded_in :city
  has_many :category
end

class City
  include Mongoid::Document

  embedded_in :share

  field :name, type: String
  field :country, type: String

  attr_accessible :name, :city_id, :id

end

Searched everywhere and I cannot figure it out. It must be something silly.