Digest::MD5

gistfile1.rb

[1] pry(main)> Digest::MD5.new.update('version-1')
=> #<Digest::MD5: e8444fc50e000a592c6f49872490349e>
[2] pry(main)> Digest::MD5.new.update('version-1').update('mini-2')
=> #<Digest::MD5: 9f328f25432758cd63ba0ddd38024364>
[3] pry(main)> Digest::MD5.new.update('version-1').update('mini-2').hexdigest
=> "9f328f25432758cd63ba0ddd38024364"

[4] pry(main)> Digest::MD5.hexdigest('version-1')
=> "e8444fc50e000a592c6f49872490349e"

[59] pry(main)> d = Digest::MD5.new.update('version-1')
=> #<Digest::MD5: e8444fc50e000a592c6f49872490349e>
[60] pry(main)> d << 'mini-2'
=> #<Digest::MD5: 9f328f25432758cd63ba0ddd38024364>
[62] pry(main)> Digest::MD5.new.update('version-1').update('mini-2').reset.update('version-1')
=> #<Digest::MD5: e8444fc50e000a592c6f49872490349e>

# object 才可以這樣chain 下去

# http://rubydoc.info/stdlib/digest/1.9.3/Digest/MD5
# http://www.ruby-doc.org/stdlib-1.9.3/libdoc/digest/rdoc/Digest/Instance.html#method-i-update
# Updates the digest using a given string and returns self.

# The update() method and the left-shift operator are overridden by each 
# implementation subclass. (One should be an alias for the other)