ruby on rails - Letting Pin select one Category -

i have problem letting pin select 1 category, below had attempted.

$ rails g model category name:string  $ rails g migration add_category_id_to_event  in /db/migrate/xxxx_add_category_id_to_pin 

i modified

class addcategoryidtopin < activerecord::migration def self.up   add_column :pins, :category_id, :integer  end  def self.down  remove_column :pin, :category_id   end  end    rake db:migrate 

in app/models/pin.rb

 class event < activerecord::base   belongs_to :category  end 

in app/models/category.rb

class category < activerecord::base  has_many :pins  end 

in rails console

category.create( :name => "course" ) category.create( :name => "meeting" ) category.create( :name => "conference" ) 

in app/views/pins/_form.html.erb

<%= f.select :category_id, category_options %> 

in pp/views/pins/show.html.erb

<p>category: <%= @pin.category.name %><p> 

in app/helpers/pins_helper.rb

module pinshelper  def category_options     category.all.map{ |c| [c.name, c.id] }  end end 

but nothing shows on app , below, before working fine. don't understand went wrong? can 1 help?

nameerror in pins#index

showing /users/mattbook/code/dine/app/views/layouts/_header.html.erb line #17 raised:

undefined local variable or method `new_pin_path' #<#:0x007f92565413d0> extracted source (around line #17):

14:
15: 16: 17: <% if user_signed_in? %>

<%= link_to "拚 +", new_pin_path %>

18:

19: 個人 20: