# File lib/simp/cli/config/items/add_server_class_action_item.rb, line 19
    def apply
      raise InternalError.new( "@class_to_add empty for #{self.class}" ) if "#{@class_to_add}".empty?

      @applied_status = :failed
      fqdn    = get_item( 'cli::network::hostname' ).value
      @file    = File.join( @dir, "#{fqdn}.yaml")

      if File.exists?(@file)
        debug( "Adding #{@class_to_add} to the class list in #{fqdn}.yaml file", [:GREEN] )
        yaml = IO.readlines(@file)

        File.open(@file, "w") do |f|
          yaml.each do |line|
            line.chomp!
            if line =~ /^classes\s*:/
              f.puts line
              f.puts "  - '#{@class_to_add}'"
            else
              f.puts line unless contains_class?(line)
            end
          end
        end
        @applied_status = :succeeded
      else
        error( "\nERROR: file not found: #{@file}", [:RED] )
      end
    end