#101 Refactoring Out Helper Object

Apr 14, 2008 | 7 minutes | Refactoring, Views

If you have complex view logic, this can easily lead to helper methods which call each other. See how to refactor this out into another object in this episode. This is also known as the presenter pattern.

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I failed to mention in the screencast, the 3 methods which aren't called externally for the object should be made private. See the code below for an example.

          application_helper.rb
                
        def render_stars(rating)
  StarsRenderer.new(rating, self).render_stars
end
        
def render_stars(rating)
  StarsRenderer.new(rating, self).render_stars
end

          helpers/stars_renderer.rb
                
        class StarsRenderer
  def initialize(rating, template)
    @rating = rating
    @template = template
  end
  
  def render_stars
    content_tag :div, star_images, :class => 'stars'
  end

  private
  
  def star_images
    (0...5).map do |position|
      star_image(((@rating-position)*2).round)
    end.join
  end
  
  def star_image(value)
    image_tag "/images/#{star_type(value)}_star.gif", :size => '15x15'
  end
  
  def star_type(value)
    if value <= 0
      'empty'
    elsif value == 1
      'half'
    else
      'full'
    end
  end
  
  def method_missing(*args, &block)
    @template.send(*args, &block)
  end
end
        
        
        
        
        
        
        
        
        
      
class StarsRenderer
  def initialize(rating, template)
    @rating = rating
    @template = template
  end
  
  def render_stars
    content_tag :div, star_images, :class => 'stars'
  end

  private
  
  def star_images
    (0...5).map do |position|
      star_image(((@rating-position)*2).round)
    end.join
  end
  
  def star_image(value)
    image_tag "/images/#{star_type(value)}_star.gif", :size => '15x15'
  end
  
  def star_type(value)
    if value <= 0
      'empty'
    elsif value == 1
      'half'
    else
      'full'
    end
  end
  
  def method_missing(*args, &block)
    @template.send(*args, &block)
  end
end