classe CustomReports.rb

class CustomReports
   def self.relatorio_geral(imobiliaria,tipo, collection, block)
    RGhost::Document.new :paper => :A4, :margin_left => 0.2, :margin_right => 0.2, :margin_bottom => 2 do |doc|
      doc.define_tags do
        tag :small,   :name => 'Verdana', :size => 12
        tag :default, :name => 'Verdana', :size => 15
        tag :title,   :name => 'Verdana', :size => 17
        tag :header1, :name => 'Verdana', :size => 20
        tag :header2, :name => 'Verdana', :size => 26
      end


      doc.before_page_create do |chunk|
        chunk.text_in :x => 1, :y => 29, :write => imobiliaria.nome, :tag => :small
        chunk.text_in :x => 16, :y => 29, :write => I18n.l(Time.now, :format => :short), :tag => :small
        chunk.text_in :x=> 18, :y=> 1, :text => "Página %current_page%", :tag => :small
      end
      2.times {doc.next_row}
      doc.show "Relatório de #{tipo.capitalize}", :with => :header2, :align => :page_center
      2.times {doc.next_row}
      doc.rails_grid :x => -3 do |grid|
        grid.even_row do |r|
          r.background_row(:content => {:fill => true, :color => '#FFF'})
        end
        grid.before_row do |r|
          r.horizontal_line(:top,    :size => 20.5 )
        end
        block.call(grid)
        grid.data(collection)
      end
     end
  end
end

view de clientes.rb

block = lambda do |grid|
    grid.column :nome,                  :title => "Nome",           :format => Default
    unless lambda{contato.blank?}
      grid.column 'contato.email',      :title => "Email",          :width => 2.5,           :format => Default
      grid.column 'contato.telefone',   :title => "Telefone",       :width => 2.5,           :format => Default
      grid.column 'contato.celular',    :title => "Celular",        :width => 2.5,           :format => Default
    end
    grid.column :cpf,                   :title => "CPF",            :width => 2,             :format => Default
    grid.column :cnpj,                  :title => "CNPJ",           :width => 2,             :format => Default
    unless lambda{endereco.blank?}
      grid.column 'endereco.bairro',    :title => "Bairro",         :width => 2.5
      grid.column 'endereco.cidade',    :title => "Cidade",         :width => 2.5
    end
end

CustomReports.relatorio_geral imobiliaria_atual, 'clientes', @clientes, block