title: Undefined method [model]_url for nested resource
body: <p>I am working on a nested resources project, and am getting an error in my steps controller:</p>
  
  <pre><code>  def create
      @step = Step.new(step_params)
  
      respond_to do |f|
        if @step.save
          f.html { redirect_to @step, notice: 'Step was successfully created.' }
          f.json { render action: 'show', status: :created, location: @step }
        else
          f.html { render action: 'new' }
          f.json { render json: @step.errors, status: :unprocessable_entity }
        end
      end
    end
  </code></pre>
  
  <p>The error I am getting is:</p>
  
  <pre><code>undefined method `step_url' for #&lt;StepsController:0x007feeb6442198&gt;
  </code></pre>
  
  <p>My routes looks like this:</p>
  
  <pre><code>root 'lists#index'
  
  resources :lists do
    resources :steps
  end
  </code></pre>