Will_Paginate on two models with both models sent together as a collection

Question

I have two models (Folder and Document) which I need to show in a single view together. However, to reduce the number of queries sent I am collecting the Documents only if the folders are less than 12 (my :per_page). While this is working fine, I am stuck in a particular case,

When my total documents are less than 12 and folders are less than 12 but together are more than 12, the pagination fails.

Below is the code to calculate which page to be shown where f_page returns the page for the Folder pagination and d_page returns the page number for the document collection.

   def f_page(page_cnt, size)
    page_cnt.present? and size.nonzero? ? page_cnt.to_i <= (size/12 + (size%12==0 ? 0 : 1)) ? page_cnt.to_i : (size / 12 ) + (size%12==0 ? 0 : 1) : 1
  end

  def d_page(page_cnt, fc, dc)
    page_cnt = page_cnt.present? ? page_cnt : 1
    puts page_cnt
    dpg = 1 
    if (fc/12+1 == page_cnt.to_i)
      dpg = 1   
    elsif ((fc/12+1) < page_cnt.to_i)
      if (fc < 12)
        unless (dc <= 12)
          dpg = page_cnt
        else
          dpg = 1
        end
        else
          (fc/12 == 0) ? (dpg = page_cnt.to_i - (fc/12+1)) : (dpg = page_cnt.to_i - (fc/12))
        end
      end
      puts "dpg = #{dpg}"
      return dpg
    end

Both are together collected and paginated which is shown in the view.

f = Folder.action_folder_collection(@action, current_user).paginate(:page => params[:page], :per_page => 12)
  if (f.count < 12)
    d = Document.action_document_collection(@action, current_user).paginate(:page => d_page(params[:page], total_folders, total_documents), :per_page => per_page-f.count)
  end
  collection << f
  collection << d
  @collection = collection.flatten.paginate(:page => 1,:per_page => 12,:total_entries => total)

How do I solve it?

sashazykov · Answer 1 · 2013-04-14T10:06:00.403

I have just solved the similar problem. My paginate_catalog_children helper receives either an AR collection or an array of collections as a parameter and returns WillPaginate::Collection object containing elements from all collections.

def paginate_catalog_children catalog_children, page
  per_page = 20
  if catalog_children.is_a? ActiveRecord::Relation
    catalog_children.paginate(:per_page => per_page, :page => page)
  else
    # paginating array of collections
    WillPaginate::Collection.create(page, per_page) do |pager|
      catalog_children_counts = catalog_children.map(&:count)

      result = []
      offset = pager.offset
      items_left = pager.per_page

      catalog_children.each_with_index do |collection, index|
        break if items_left == 0
        if catalog_children_counts[index] <= offset
          # skip this collection
          offset -= catalog_children_counts[index]
        else
          collection_items = collection.limit(items_left).offset(offset)
          result += collection_items
          items_left -= collection_items.size
          offset = 0
        end
      end

      pager.replace(result)
      pager.total_entries = catalog_children_counts.sum
      result
    end
  end
end

Will_Paginate on two models with both models sent together as a collection

1 Answers1