Introduction to DDD

1. Domain Driven Design
Primer

2. The
Communication
Chasm

3. Reduce Verbal Friction

4. DDD and it’s components

5. Ubiquitous Language

6. Sounds Easy

7. It’s not

8. Technical Terms

9. class Customer {
public string Cust_Name {…}
}

10. class CustomerFactory {
…
}

11. Not Just Class Names

12. Industry vs Business
Nomenclatures

13. class GobbleGobble {
…
}
// or
class Turkey {
…
}

14. Fluency

15. invoice.ChangeShipDateTo
(newShipDate)

16. Code Impact

17. Aggregate Roots

18. Purchaser
Invoice
Ship To
Address Items
Product Discount
Code
Tax
Code
Billing
Address

19. Many per Application

20. Overlap

21. Invoice
vs
Statement.Invoice

22. Clarity > Reuse

23. Context is King

24. Encapsulation

25. class Invoice {
public List<InvoiceItem> Items
{ get; set; }
}
invoice.Items.Add
(new InvoiceItem);

26. class Invoice {
private List<InvoiceItem> _items;
public IEnumerable<InvoiceItem> Items
{ get {return _items;}}
public void AddItem(InvoiceItem item) {
_items.Add(item);
//change invoice total
//change invoice tax totals
//change invoice item count
}
}

27. class Invoice {
public void ChangeShippingAddressTo(
ShippingAddress newAddress) {
//change address
//add change fee
//etc.
}
}

28. invoice.ShippingAddress.XXX =
“blah”;
var xyz =
invoice.ShippingAddress.XXX;

29. Data Access

30. UI
Service Layer
Domain Model
Data Access

31. Only via Aggregate Roots

32. Load aggregate root
Modify values
Persist aggregate root

33. But now we’re loading things
we might not need/use…

34. Use an ORM

35. Lazy Loading

36. DDD anti-patterns

37. Anemic Domain Model

38. Default constructors

39. 1 Repository class
:
1 Domain class

40. Domain model in the UI

41. Auto-mapping
from
UI -> Domain model

42. Public property setters

43. What will happen
when you try DDD?

44. You’ll have to talk to the
business more

45. The business will talk to you
just like your code reads

46. You will struggle
to give up the
“One model to rule them all”

47. Large, complex systems
will seem simpler

48. Find it hard to keep the
model out of the UI

49. Have difficulties when
reading data for display

50. Erroneously try to use DDD
everywhere

51. donald.belcham@igloocoder.com
@dbelcham
www.igloocoder.com