The document emphasizes the importance of writing maintainable code that stands the test of time, advocating for improved comprehension, flexibility, and testing. It outlines practical coding principles, such as adhering to single responsibility and avoiding premature optimization, alongside promoting object calisthenics as a method for improving coding skills. Additionally, it encourages continuous learning through reading and sharing code with others.

1. Writing code
that lasts.
Rafael Dohms
@rdohms
photo: djandyw.com

2. Writing code
you won’t hate tomorrow.
Rafael Dohms
@rdohms
photo: djandyw.com

3. Lead Backend Engineer
Rafael Dohms
jobs.usabilla.com
@rdohms on twitter

4. Lead Backend Engineer
Rafael Dohms
jobs.usabilla.com
FeedbackFeedback
@rdohms on twitter

6. photo: Rob Allen (@akrabat)

8. REWRITE
ALL THE CODE!
image: hyperboleandahalf

9. Real Developers,
SHIP STUFF.
photo: Glyn Lowe Photoworks

13. How do we find
balance?
photo: Kalexanderson

14. Code has an
expiration date
photo: CarbonNYC

15. Code is
perishable, it rots.
photo by: massdistraction

16. Code Evolves
photo by: kevin dooley

17. Languages evolve.
photo by: raneko

18. You evolve.
photo by: Kaptain Kobold

19. Complexity
kills
Comprehension
photo: osbornb

20. Bad Design
photo: miskan

21. Bad specs

22. NIH
source: Urban dictionary
photo by: John 'K'

23. NIH
| nɒt ɪnˈventɪd hɪə |
Not Invented Here —The German art of humiliating any technology,
agricultural product, or (medical) scientific work that has not been
invented or produced in Germany, Switzerland, or Austria.
source: Urban dictionary
photo by: John 'K'

24. The Solution™
photo: Ian Sane

25. Improve code

26. Improve code
make it easier to comprehend

27. Improve code
make it easier to comprehend
make it flexible

28. Improve code
make it easier to comprehend
make it flexible
make it tested

29. Improve code
make it easier to comprehend
make it flexible
make it tested
make it easier to replace, refactor

30. Improve code
make it easier to comprehend
make it flexible
make it tested
make it easier to replace, refactor
make it not exist

31. Testing
photo by: jeffkrause

32. "Refactoring without tests
is just changing stuff."

33. Good Design
Concepts

34. Single Responsibility
Open and Close
Liskov substitution
Interface Segregation
Dependency Inversion
Singleton
Tight Coupling
Untestability
Premature Optimization
Indescriptive Naming
Duplication
Solid Stupid
○"

35. Design Patterns
photo by halloweenstock

36. Domain Driven Design
with Ubiquitous Language
photo by lwr

37. Modular Architecture
CQRS, Event Sourcing, Micro Services
photo by medialoog

38. Package
Managers

39. PIE
Proudly
Invented
Elsewhere

40. photo by: boston_public_library
Object Calisthenics
Jeff Bay

41. Calisthenics
/ˌkaləsˈTHeniks/
Calisthenics are a form of dynamic exercise consisting of a variety of
simple, often rhythmical, movements, generally using minimal
equipment or apparatus.
photo by: boston_public_library

42. These are
exercises, not rules. photo by: david_a_l

43. #1
Only one
indentation level
per method.
photo by: justinliew

44. #2
Do not
use else
photo by: justinliew

45. public function createPost($request)
{
$entity = new Post();
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid()){
$repository = $this->getRepository('MyBundle:Post');
if (!$repository->exists($entity) ) {
$repository->save($entity);
return $this->redirect('create_ok');
} else {
$error = "Post Title already exists";
return array('form' => $form, 'error' => $error);
}
} else {
$error = "Invalid fields";
return array('form' => $form, 'error' => $error);
}
}

46. public function createPost($request)
{
$entity = new Post();
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid()){
$repository = $this->getRepository('MyBundle:Post');
if (!$repository->exists($entity) ) {
$repository->save($entity);
return $this->redirect('create_ok');
} else {
$error = "Post Title already exists";
return array('form' => $form, 'error' => $error);
}
} else {
$error = "Invalid fields";
return array('form' => $form, 'error' => $error);
}
}
actual goal of function
“Create Post"

47. public function createPost($request)
{
$entity = new Post();
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid()){
$repository = $this->getRepository('MyBundle:Post');
if (!$repository->exists($entity) ) {
$repository->save($entity);
return $this->redirect('create_ok');
} else {
$error = "Post Title already exists";
return array('form' => $form, 'error' => $error);
}
} else {
$error = "Invalid fields";
return array('form' => $form, 'error' => $error);
}
}
this is all
error
handling

48. public function createPost($request)
{
$entity = new Post();
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid()){
$repository = $this->getRepository('MyBundle:Post');
if (!$repository->exists($entity) ) {
$repository->save($entity);
return $this->redirect('create_ok');
} else {
$error = "Post Title already exists";
return array('form' => $form, 'error' => $error);
}
} else {
$error = "Invalid fields";
return array('form' => $form, 'error' => $error);
}
}

49. public function createPost($request)
{
$entity = new Post();
$repository = $this->getRepository('MyBundle:Post');
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid() === false){
return array('form' => $form, 'error' => 'Invalid fields');
}
if ($repository->exists($entity)){
return array('form' => $form, 'error' => 'Duplicate post
title');
}
$repository->save($entity);
return $this->redirect('create_ok');
}

50. public function createPost($request)
{
$entity = new Post();
$repository = $this->getRepository('MyBundle:Post');
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid() === false){
return array('form' => $form, 'error' => 'Invalid fields');
}
if ($repository->exists($entity)){
return array('form' => $form, 'error' => 'Duplicate post
title');
}
$repository->save($entity);
return $this->redirect('create_ok');
}
exit condition 1: invalid form

51. public function createPost($request)
{
$entity = new Post();
$repository = $this->getRepository('MyBundle:Post');
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid() === false){
return array('form' => $form, 'error' => 'Invalid fields');
}
if ($repository->exists($entity)){
return array('form' => $form, 'error' => 'Duplicate post
title');
}
$repository->save($entity);
return $this->redirect('create_ok');
}
exit condition 2: duplicated post

52. public function createPost($request)
{
$entity = new Post();
$repository = $this->getRepository('MyBundle:Post');
$form = new MyForm($entity);
$form->bind($request);
if ($form->isValid() === false){
return array('form' => $form, 'error' => 'Invalid fields');
}
if ($repository->exists($entity)){
return array('form' => $form, 'error' => 'Duplicate post
title');
}
$repository->save($entity);
return $this->redirect('create_ok');
}
this is what the
method actually
does

53. public function createPost($request)
{
$repository = $this->getRepository('MyBundle:Post');
$entity = new Post();
$repository->save($entity);
return $this->redirect('create_ok');
}

54. public function createPost($request)
{
$repository = $this->getRepository('MyBundle:Post');
$entity = new Post();
$repository->save($entity);
return $this->redirect('create_ok');
}
FormValidationMiddleware
UniqueEntityMiddleware

55. public function createPost($request)
{
$repository = $this->getRepository('MyBundle:Post');
$entity = new Post();
$repository->save($entity);
return $this->redirect('create_ok');
}
The power of PSR-7
and middleware
FormValidationMiddleware
UniqueEntityMiddleware

58. #3
Wrap primitive
types, if they
contain behavior
photo by: justinliew

59. $component->repaint(false);

60. $component->repaint( new Animate(false) );

61. use MoneyMoney;
$fiveEur = Money::EUR(500);
$tenEur = $fiveEur->add($fiveEur);

62. #4
Only one
-> per line
photo by: justinliew

63. $user = $this->get('security.token_storage')->getToken()->getUser();

64. $user = $this->get('security.token_storage')->getToken()->getUser();
null

65. #5
Do not
abbreviate.
photo by: justinliew

66. if($sx >= $sy) {
if ($sx > $strSysMatImgW) {
$ny = $strSysMatImgW * $sy / $sx;
$nx = $strSysMatImgW;
}
if ($ny > $strSysMatImgH) {
$nx = $strSysMatImgH * $sx / $sy;
$ny = $strSysMatImgH;
}
}

67. #6
Keep your
classes small.
photo by: justinliew

68. #7
Limit your
instance
variables to 2
photo by: justinliew

69. class MyRegistrationService
{
protected $userService;
protected $passwordService;
protected $logger;
protected $translator;
protected $entityManager;
protected $imageCropper;
// ...
}

70. #8
Use first class
collections
photo by: justinliew

71. #9
Don’t use getters
and setters.
photo by: justinliew

72. public function getScore($request)
{
return $this->score;
}
public function setScore($score)
{
$this->score = $score;
}
$game->setScore($game->getScore() += 1);

73. public function collectedCoin()
{
$this->score += 1;
}
$game->collectedCoin();

74. #10
Document
your code.
photo by: justinliew

75. Your turn.

76. Improve
yourself!

77. Read lots of
code!

78. Write simpler
code.

79. Try Object Calisthenics
for a month.

80. Use someone
else’s code,
and share yours!

81. Thank you.
http://slides.doh.ms
http://doh.ms
@rdohms
jobs.usabilla.com
looking for a job in Amsterdam?

82. http://l.doh.ms/object-calisthenics-links
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