A look at how splitting up your models as they change can make them stricter, stronger and easier to understand. A lightning talk done for DomCode

1. Object Invariants,
Immutability & You
Making Objects Do Your Bidding
Domcode 26-11-2014

2. Jeroen v.d. Gulik
• CTO / Founder Isset (http://isset.nl)
• Builder of Artificial Stupidity
• @n0x13
• Likes Cats … a lot

3. “Every Great talk should
start with a Quote”
- Ross Tuck

4. Telephone Game

5. “People Lie, therefore
Objects Lie”
- Jeroen v.d. Gulik

6. Objects as dumb data
stores
This is our industry standard

9. Context and Intent get lost
- Ronald Reagan

10. Objects should have
behaviour attached to
them
- Mao Zedong

14. Objects should tell a tale about its
current state and all the possible
ways to change that state
- Adolf Hitler

18. Objects should be
responsible for their own
internal consistency

19. Schrödinger's cat
- Michael Jackson

20. Make the Implicit,
Explicit

21. UnpaidOrder PaidOrder

24. “Sounds like a State Machine”
- Igor Wiedler

25. Immutability

26. UnpublishedArticle PublishedArticle

27. UnpublishedArticle PublishedArticle
Draft Article

29. Draft Article RetractedArticle

31. Magic is bad, hmmmkay
- Mahatma Ghandi

32. Objects should …
• Be responsible for their own internal state
• Have specific behaviour towards its
responsibility
• Broadcast their state
• Only care about the state it’s currently in.

33. Questions?

34. Please rate my talk:
https://joind.in/12818