Trims ruby string to set length maintaining full words

Ruby String Trim at Full Word

def desc_trim
    @string = self.description.to_s
    @max = 120
    if @string
      if @string.size > @max
        @words = @string.split(' ')
        @end = "..."
        @output = ''
        i = 0
        @words.each_with_index do |w, i|    
          @length = @output.size + w.size
          begin
            if @length < @max
              @output = @output + " " + w
            end
          rescue
            puts "!!!longer!!!"
          end
        end
        @output = @output + @end.to_s
      else
        @output = @string
      end
      @output
    else
      ''
    end
  end