Before objects are marshaled, and after they've been loaded, Ruby will attempt to call marshal_dump and marshal_load on that object. This can be used to prevent unnecessary dumping of member variables, and to allow objects with un-marshalable objects to be marshaled. In the following example, a Log class stores the filename of a log file only. When it's unmarshaled, it will re-open this log file for appending.
#!/usr/bin/env ruby
class Logfile
def initialize(filename)
@filename = filename
# This IO object can't be marshaled
@io = File.open(filename,'w')
end
def marshal_dump
log "Being marshaled"
# Dump just the filename, leave the IO object alone
@filename
end
def marshal_load(filename)
@filename = filename
@io = File.open(@filename, 'a');
log "Unmarshaled"
end
def log(message)
@io.puts "#{Time.now}: #{message}"
end
end
logfile = if File.exists?('logfile')
File.open('logfile') do|file|
Marshal.load(file)
end
else
Logfile.new('log.txt')
end
ARGV.each do|message|
logfile.log message
end
File.open('logfile','w') do|file|
Marshal.dump(logfile, file)
end
