title: No route matches [POST] in nested routes for form_for helper
body: <p>I am trying to submit a form for and keep running into this error:</p>
  
  <pre><code>No route matches [POST]
  </code></pre>
  
  <p>here is my form:</p>
  
  <pre><code>&lt;%= form_for(@issue) do |f| %&gt;
      &lt;%= render 'fields', :f =&gt; f %&gt;
      &lt;div class="actions"&gt;
          &lt;%= f.submit "Submit" %&gt;
      &lt;/div&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>and my routes:</p>
  
  <pre><code>  resources :apps do
      resources :issues
    end
  </code></pre>
  
  <p>I think i'm missing something with defining which app it is in the form_for but im not sure?</p>
  
  <p>here's my issue create action:</p>
  
  <pre><code>  def create
      @issue = Issue.new(params[:issue])
      @issue.app_id = params[:app_id]
      if @issue.save
        flash[:success] = "Issue added!"
        redirect_to @issue
      else
        render 'new'
      end
    end
  </code></pre>