Last Updated: 2024-04-25

I showed J my ProductController in Rails, which was as follows:

def show
  cache_publicly

  @notes_file_count = product.notes_files.count
  @author_count = product.notes_files.pluck(:author).uniq.count
  @average_page_count = average_page_count(@author_count)
  @sale_count = @product.sales.count
  @hit_count = Traffic.new.hits_to_product(@product.id)
  @sale_rank = SaleRank.new.of_product(@product)
  @satisfaction_percentage = satisfaction_percentage
  @bundle_product = @product.bundle_product

  @notes_files = @product.notes_files.with_attached_sample.with_attached_image
    .reorder(released_on: :desc).limit(15)
  render :show
end

private

def satisfaction_percentage
end
def average_page_count
end

I lamented the number of instantiations within and he suggested I look into what we called a presenter pattern (but I myself might name "an assembler" pattern) such that I have one instatiation.

class IndividualProductPresenter
  def sales_rank
  end

  def average_page_count
  end

  def notes_files
  end
end

Evaluating

Pros

• Controller easier to set up for tests
• The new presenter object could be tested in the console with more ease.

Cons

• I add an additional layer
• Naming might be hard (e.g. other actions in the ProductsController use the same private methods)

Resources

• http://blog.jayfields.com/2007/03/rails-presenter-pattern.html