This document discusses various programming concepts and techniques including: - Object oriented design and whether it makes programming more enjoyable - Techniques for working with dates like DateTime parsing and date arithmetic - Addressing anemic domain models by adding behavior to entities - Different approaches to application architecture like repositories, services, and the unit of work pattern - Best practices for testing like focusing tests on behavior rather than implementation details - Principles like abstraction, the story of the code, and only coding what is needed

1. Who killed
Object Oriented
Design?

2. Colonel PHP
with a lead pipe in
the study?

3. Just look around...

4. Is OOD making
programming more
enjoyable?

5. How many abstract
classes have you
written lately?

6. When was the last
time that you had a
design meeting?

7. Which one is your
favorite LINQ
expression?

8. Why would you use
yield or yield
return?

9. Primitive
Addiction

10. Be lazy

11. Make your life easier

12. Avoid repetition

13. Use the source Luke

14. Creating dates is
painful?

15. DateTime.Parse("...")

16. new DateTime(y, m, d)

17. On.Jan(1)
On.Aug(3, 2013)

18. Date arithmetic makes
you crazy?

19. DateTime.Today.AddDays(-3)

20. 3.Days().Ago

21. 5.Days().Span

22. 1.Month().Ago +
5.Days().Span

23. On.Dec(10) - 2.Months().Span

24. 2.Months().Before(On.Dec(10))

25. Date from and to in
every method?

26. What’s missing?

27. Use a DateRange

28. new DateRange(
!!!!!!On.Jul(1),
!!!!!!1.Month().Span)

29. public class DateRange:
!!!!!IEnumerable<DateTime>

30. var r = new DateRange(
!!!!!!!!!!!!!!On.Jul(1),
!!!!!!!!!!!!!!On.Sep(3))
r.Select(d => ....)

31. Generates a sequence
of dates

32. public IEnumerator<DateTime> GetEnumerator()
{
var counter = this.StartDate;
while (counter <= this.EndDate)
{
yield return counter;
counter = counter.AddDays(1);
}
}

33. Anemic models

34. OO mixes behavior
and data

35. Models usually
represent data

36. ...and you realize that there
is hardly any behavior on
these objects, making them
little more than bags of
getters and setters...
Martin Fowler

37. Rich vs Anemic

38. What about SOLID?

39. Can we justify more
classes?

40. Validators
Processors
Retrievers
Translators
Services
Builders

41. class WorkingShift
{
public Code { get; set; }
public Desc { get; set; }
}

42. Night, day or evening...
Who’s responsible?

43. shift.Code == "NIGHT"

44. class WorkingShift
{
public Code { get; set; }
public Desc { get; set; }
public bool IsNight() { ... }
}

45. class Customer
{
public IsOfDrivingAge { get; }
}

46. How to decide?

47. Functionality is
Complex

48. Functionality uses
multiple models

49. Interacting with
external service

50. Is not a core
concern

51. Multiple ways of
implementation

52. Some options

53. Use extensions

54. public static class CustomerExtensions
{
public static bool
! ! ! ! IsOfDrivingAge(this Customer ...)
}

55. Decorator

56. View Model

57. Service Objects

58. Form Objects

59. Repository
overpopulation

60. Mediates between the
domain and data mapping
layers using a collection-like
interface for accessing
domain objects
Martin Fowler

61. public interface IRepository<T>
{
IEnumerable<T> All();
void Insert(T entity);
void Delete(T entity);
}

62. Custom queries

63. class CustomerRepository:
! ! ! IRepository<Customer>
{
// Implementation interface
IEnumerable<Customer> FindByAddr(Address )
}

64. CustomerRepository
AddressRepository
ChairRepository
...

65. IQueryable<T>

66. public interface IRepository<T>
{
IQueryable<T> All();
void Insert(T entity);
void Delete(T entity);
}

67. class CustomerExtensions
{
public IQueryable<Customer> FindByAddress(
this IQueryable<Customer> query,
Address address)
{
query.Where(c => c.Address == address)
}
}

68. How many
repositories?

69. Only one generic
implementation on top
of your favorite ORM

70. IOC container can
instantiate the right one

71. UnitOfWork
can be a factory of
repositories

72. Having an ORM do we
really need a
repository?

73. Testing the
testable test is
tested

74. A test is about behavior

75. Not implementation

76. Writing expectations
about implementation
makes it brittle

77. public int ImportantMethod()
{
var c1 = _dependency1.Calculate();
var c2 = _dependency2.Adjust(c1);
return c2 + 10;
}

78. public void ImportantTest()
{
// arrange ....
_dependency1
! ! ! .Expect(d => d.Calculate())
! ! ! .Once()
! ! ! .AndReturn(50)
_dependency2
! ! ! .Expect(d => d.Adjust(50))
! ! ! .Once()
! ! ! .AndReturn(100)
// act
var actual = sut.ImportantMethod()
// assert
Assert.That(actual, Is.EqualTo(110))
! VerifyAllExpectations()
}

79. public int ImportantMethod()
{
var c1 = _dependency1.Calculate();
var c2 = _dependency2.Adjust(c1);
return _dependency2.Adjust(c1) + 10;
}

80. public void ImportantTest()
{
// arrange ....
_dependency1
! ! ! ! .Stub(d => d.Calculate())
! ! ! ! .AndReturn(50)
_dependency2
! ! ! ! .Stub(d => d.Adjust(50))
! ! ! ! .AndReturn(100)
// act
var actual = sut.ImportantMethod()
// assert
Assert.That(actual, Is.EqualTo(110))
}

81. Abstraction
subtraction

82. Exercise in groups

83. Hospital Domain Model

84. Versions

85. What the domain
looked like
X months ago

86. DB Driven
Development

87. Model may or may not
match the database

88. Active Record

89. Transaction Script

90. Data Mapper

91. Coding is like
Telling a Story

92. Leave the code cleaner
than you found it

93. Meaning is KING

94. Don’t code what you
don’t need

95. Know your
collections

96. Let LINQ do the work
for you

97. Use extension methods
to mimic a DSL

98. Discuss design
options

99. Explore F#

100. Thank you!

101. http://smartviewapp.com
The Smartest tool
for lean project
management

102. amir@barylko.com
@abarylko
http://bit.ly/abarylkoslides

103. Photo Credit
• Under http://creativecommons.org/licenses/by/2.5/
• Joe Cheng, DSC_7820-01, http://flic.kr/p/2Zt2u
• Bill Ward, Derek Schin's Trucks 1, http://flic.kr/p/m5L5S
• Jeremy Keith, Roast beef, http://flic.kr/p/TKUz
• Rob Campbell, Field of daisies, http://flic.kr/p/6QJjU4
• Karin Dalziel, The Thinker, http://flic.kr/p/4UYArc

104. Photo Credit 2
• Under https://creativecommons.org/licenses/by-sa/2.0/
• Don LaVange, To Irene, https://flic.kr/p/49ihZX
• Under http://creativecommons.org/licenses/by-sa/3.0/us/
• Derick Bailey, SOLID Motivational Posters, http://bit.ly/17aVaHg
• MGA Roadster 1600 in Chariot Red: http://www.carandclassic.co.uk/car/C414652
• Cone of Uncertainty, http://www.agilenutshell.com/cone_of_uncertainty
• Burning Money, http://en.wikipedia.org/wiki/Money_burning#mediaviewer/
File:Burning-money-and-yuanbao-at-the-cemetery-3249.JPG