Ruby on Rails: a weird no method error in my controller?

Here's what I got in my logs:

Started POST "/video_votes.437?type=up" for 127.0.0.1 at Fri Mar 18 01:11:14 -0700 2011 Processing by VideoVotesController#create as Parameters: {"authenticity_token"=>"DLyDcc4MJxK7gk4URiyyjvsLLl9hjtDChAyQRGVawKg=", "type"=>"up"} Com开发者_如何学编程pleted in 83ms

NoMethodError (You have a nil object when you didn't expect it! You might have expected an instance of ActiveRecord::Base. The error occurred while evaluating nil.[]): app/controllers/video_votes_controller.rb:3:in `create'

I get this error when I click the button that calls on the create method.

Here's the code in my create method (note that line three is the @video = Video.find(params[:video_vote][:video_id]) line):

def create       
  @video = Video.find(params[:video_vote][:video_id])
  @vote = @video.video_votes.new
  if params[:type] = "up"
    @vote.value = 1
  else
    @vote.value = -1
  end

  if @vote.save
    respond_to do |format|
      format.html { redirect_to @video }
      format.js
    end
  else
    respond_to do |format|
      format.html { redirect_to @video }
      format.js {render 'fail_create.js.erb'}
    end
  end

And here's my code for the button in my view that calls the create method:

<div id='voting_div'>
  <%= button_to "+1", video_votes_path(video, :type=> "up"), :remote => true %>
  <div id='vote_display'>
    <p id='votes'><%= pluralize video.vote_sum, 'Votes' %></p>
  </div>
  <%= button_to "-1", video_votes_path(video, :type=> "down"), :remote => true %>
</div>

What's going on here? How do I fix this error?

You params hash is {"authenticity_token"=>"DLyDcc4MJxK7gk4URiyyjvsLLl9hjtDChAyQRGVawKg=", "type"=>"up"}

In this hash there is no key called "video_vote" , so when you try to access params[:video_vote][:video_id], because params[:video_vote] is nil. it will throw this error.

Check your routes or if you need to "GET" more values with the button, because your params hash doesn't know about the "video_vote" key.