serialize.rb

class Human 
   
  attr_accessor :name, :age
  
  def initialize(name, age)
    @name = name 
    @age = age
  end
  
  # Serialization (to JSon) by hand
  def to_json
    "{\"name\": \"#{@name}\", \"age\": #{@age}}"
  end
  
  # Dump in  file (using Marshal)
  def to_file(file)
    File.open(file, 'wb') do | channel |
      serialized = Marshal.dump(self)
      channel.write(serialized)
    end
  end
  
  # Load from file (using Marshal)
  def self.from_file(file)
    File.open(file, 'rb') do | channel | 
      Marshal.load(channel)
    end
  end
end

usage.rb

# Initialize data
xavier = Human.new('Xavier', 28)
antoine = Human.new('Antoine', 34)

# Serialize to Json
puts xavier.to_json
puts antoine.to_json

# Dump into a file 
xavier.to_file('xavier.data')
antoine.to_file('antoine.data')

# Retreive data from a file
xavier2 = Human.from_file('xavier.data')
antoine2 = Human.from_file('antoine.data')