gistfile1.txt

## code
  def listing_file=(file)
    # self.listing_files.build.attachment = file
    self.listing_files.create :attachment => file
    self.listing_files.build(:attachment => file)
    raise "
    
    #{file}
    
    ----
    #{self.listing_files.first.attachment}
    #{self.listing_files.last.attachment = file}
    #{self.listing_files.last.attachment}
    
    
    "
  end


## output
    attachment#<File:0x37f4178>
    
    ----
    /attachments/original/missing.png
    attachment#<File:0x37f4178>
    /attachments/original/missing.png