Presentation made at GTA meetup in 2012-02-07. Object Calisthenics is a set of exercise rules to reach better code, maintainable, testable and readable.

1. Object Calisthenics
Applied to PHP

2. Object Calisthenics
The speaker
@guilhermeblanco
http://github.com/guilhermeblanco

3. Object Calisthenics
Agenda
‣ Motivation
‣ Rules
‣ Application

4. Object Calisthenics
Erm... WTH is Object Calisthenics?
‣ Object Calisthenics

5. Object Calisthenics
Erm... WTH is Object Calisthenics?
‣ Object Calisthenics
Term derived from greek,
“exercise”, under the
context of gymnastics.

6. Object Calisthenics
Erm... WTH is Object Calisthenics?
‣ Jeff Bay in The ThoughtWorks Anthology [1]
coined the term Object Calisthenics in computers,
as a group of exercises to Object Oriented
programming.
[1] The ThoughtWorks Anthology: Essays on Software Technology and Innovation

7. Object Calisthenics
Motivation
‣ Readable Code
‣ Comprehensible
‣ Testable
‣ Maintainable
Learning about good code practices
at Object CaIisthenics talk of
@guilhermeblanco on @gtaphp

8. Object Calisthenics
Rules
‣ Nine (9) rules “very” simple...

9. Object Calisthenics
Rule 1: Only one indentation level per method
‣ Only one indentation level per method

10. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ($input->hasInvalid() || $input->hasMissing()) {
foreach ($input->getMessages() as $field => $messageList) {
foreach ($messageList as $message) {
if (strpos($message, "empty")) {
throw new Tss_FormException(
"The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
throw new Tss_FormException(
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}
return $input;
}

11. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
0 if ($input->hasInvalid() || $input->hasMissing()) {
1 foreach ($input->getMessages() as $field => $messageList) {
2 foreach(strpos($message, "empty")) {
($messageList as $message) {
3 if throw new Tss_FormException(
4 "The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
throw new Tss_FormException(
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}
return $input;
}

12. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
0 if ($input->hasInvalid() || $input->hasMissing()) {
1 foreach ($input->getMessages() as $field => $messageList) {
2 foreach(strpos($message, "empty")) {
($messageList as $message) {
3 if throw new Tss_FormException(
4 "The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
throw new Tss_FormException(
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}
return $input;
}

13. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
foreach ($input->getMessages() as $field => $messageList) {
foreach ($messageList as $message) {
if (strpos($message, "empty")) {
throw new Tss_FormException(
"The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
throw new Tss_FormException(
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}

14. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
0 foreach ($input->getMessages() as $field => $messageList) {
1 foreach(strpos($message, "empty")) {
($messageList as $message) {
2 if throw new Tss_FormException(
3 "The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
throw new Tss_FormException(
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}

15. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
foreach ($input->getMessages() as $field => $messageList) {
foreach ($messageList as $message) {
$errorMessage = (strpos($message, "empty") === false)
? "The field {$field} cannot be empty!"
: "{$message}";
throw new Tss_FormException(
$errorMessage, 3, 'javascript:history.back();'
);
}
}
}

16. Object Calisthenics
Rule 1: Only one indentation level per method
public function validateForm($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
0 foreach ($input->getMessages() as $field => $messageList) {
1 foreach ($messageList as $message) { "empty") === false)
2 $errorMessage = (strpos($message,be empty!"
? "The field {$field} cannot
: "{$message}";
throw new Tss_FormException(
$errorMessage, 3, 'javascript:history.back();'
);
}
}
}

17. Object Calisthenics
Rule 1: Only one indentation level per method
public function validatePost($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
foreach ($input->getMessages() as $field => $message) {
$messageKey = key($message);
$message = $message[$messageKey];
$errorMessage = (strpos($message, "empty") === false)
? "The field {$field} cannot be empty!"
: "{$message}";
throw new Tss_FormException(
$errorMessage, 3, 'javascript:history.back();'
);
}
}

18. Object Calisthenics
Rule 1: Only one indentation level per method
public function validatePost($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data, $options);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
foreach ($input->getMessages() as $field => $message) {
$messageKey = key($message);
$message = $message[$messageKey];
$errorMessage = (strpos($message, "empty") === false)
? "The field {$field} cannot be empty!"
: "{$message}";
throw new Tss_FormException(
$errorMessage, 3, 'javascript:history.back();'
);
}
}

19. Object Calisthenics
Rule 2: Do not use the “else” keyword
‣ Never use the “else” keyword

20. Object Calisthenics
Rule 2: Do not use the “else” keyword
function login() {
$login = $this->input->post('email', true);
$password = $this->input->post('password', true);
$reference = $this->input->post('reference', true);
if ($this->clients_model->login($login, $password)) {
redirect($reference);
} else {
$this->session->set_flashdata('error', 'User or password invalid.');
$this->session->set_flashdata('reference', $reference);
redirect('clients');
}
}

21. Object Calisthenics
Rule 2: Do not use the “else” keyword
function login() {
$login = $this->input->post('email', true);
$password = $this->input->post('password', true);
$reference = $this->input->post('reference', true);
if ($this->clients_model->login($login, $password)) {
redirect($reference);
} else {
$this->session->set_flashdata('error', 'User or password invalid.');
$this->session->set_flashdata('reference', $reference);
redirect('clients');
}
}

22. Object Calisthenics
Rule 2: Do not use the “else” keyword
function login() {
$login = $this->input->post('email', true);
$password = $this->input->post('password', true);
$reference = $this->input->post('reference', true);
if ($this->clients_model->login($login, $password)) {
redirect($reference);
} else {
$this->session->set_flashdata('error', 'User or password invalid.');
$this->session->set_flashdata('reference', $reference);
redirect('clients');
}
}

23. Object Calisthenics
Rule 2: Do not use the “else” keyword
function login() {
$login = $this->input->post('email', true);
$password = $this->input->post('password', true);
$reference = $this->input->post('reference', true);
if ( ! ($this->clients_model->login($login, $password))) {
$this->session->set_flashdata('error', 'User or password invalid.');
$this->session->set_flashdata('reference', $reference);
$reference = 'clients';
}
redirect($reference);
}

24. Object Calisthenics
Rule 3: Wrap primitive types and strings
‣ Wrap all primitive types and strings

25. Object Calisthenics
Rule 3: Wrap primitive types and strings
‣ This rule cannot be completely ported to PHP, because
the language does not perform well with an entirely
Object Oriented code with a huge amount of instances

26. Object Calisthenics
Rule 3: Wrap primitive types and strings
‣ But... if the variable of primitive type has a behavior, it
must be encapsulated

27. Object Calisthenics
Rule 3: Wrap primitive types and strings
class UIComponent
{
! // ...
!
public function repaint($animate = true)
{
// ...
}
}
// ...
$component->repaint(false);

28. Object Calisthenics
Rule 3: Wrap primitive types and strings
class UIComponent
{
! // ...
!
public function repaint($animate = true)
{
// ...
}
}
// ...
$component->repaint(false);

29. Object Calisthenics
Rule 3: Wrap primitive types and strings
class UIComponent
{
! // ...
!
public function repaint(Animate $animate)
{
// ...
}
}
class Animate
{
public $animate;
public function __construct($animate = true)
{
$this->animate = $animate;
}
}
// ...
$component->repaint(new Animate(false));

30. Object Calisthenics
Rule 4: Only one dot per line
‣ Only one dot (arrow for PHP) per line

31. Object Calisthenics
Rule 4: Only one dot per line
‣ Not applicable to PHP...

32. Object Calisthenics
Rule 4: Only one dot per line
‣ ...but multiple nested calls...
‣ tend to expose an encapsulation problem
‣ increase difficulty to debug and exception handling
‣ do not represent an atomic action

33. Object Calisthenics
Rule 4: Only one dot per line
‣ We could adapt to the language, contemplating...

34. Object Calisthenics
Rule 4: Only one dot per line
‣ A chain of different objects, but only if the execution
only includes getters and setters
$user->getLocationPoint()->getCountry()->getName();

35. Object Calisthenics
Rule 4: Only one dot per line
‣ A chain of a unique object, through the usage of a
fluent interface
$filterChain->addFilter(new Zend_Filter_Alpha())
->addFilter(new Zend_Filter_StringToLower());

36. Object Calisthenics
Rule 5: Do not abbreviate
‣ Do not abbreviate

37. Object Calisthenics
Rule 5: Do not abbreviate

38. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?

39. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?
‣ Write the same name repeatedly?

40. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?
‣ Write the same name repeatedly?
‣ Then your method is reused multiple times,
signalling a code duplication.

41. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?
‣ Write the same name repeatedly?
‣ Then your method is reused multiple times,
signalling a code duplication.
‣ Method name too long?

42. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?
‣ Write the same name repeatedly?
‣ Then your method is reused multiple times,
signalling a code duplication.
‣ Method name too long?
‣ Maybe your class has multiple responsibilities or it
is missing a helper class (bad architecture).

43. Object Calisthenics
Rule 5: Do not abbreviate
‣ Think about it... why do you want to abbreviate?
‣ Write the same name repeatedly?
‣ Then your method is reused multiple times,
signalling a code duplication.
‣ Method name too long?
‣ Maybe your class has multiple responsibilities or it
is missing a helper class (bad architecture).

44. Object Calisthenics
Rule 6: Keep your entities small
‣ Keep your entities small

45. Object Calisthenics
Rule 6: Keep your entities small
‣ Original rule: 50 lines per class

46. Object Calisthenics
Rule 6: Keep your entities small
‣ Adapted to PHP: 100 lines per class and no more than
15 classes per package.
‣ The change is necessary because of the lack of rule for
documentation, which can easily occupy up to 50% of
the lines of a class.

47. Object Calisthenics
Rule 7: Do not create classes with more than 2 instance variables
‣ Do not create classes with more than 2 instance
variables

48. Object Calisthenics
Rule 7: Do not create classes with more than 2 instance variables
‣ Objective:
‣ Low cohesion
‣ Better encapsulation

49. Object Calisthenics
Rule 7: Do not create classes with more than 2 instance variables
‣ The original rule points to 2 instance variables
‣ To PHP, the suggestion is no more than 5 variables

50. Object Calisthenics
Rule 8: Use first class collections
‣ Use first class collections

51. Object Calisthenics
Rule 8: Use first class collections
‣ The rule is simple: Any class that contains a collection
(array to PHP), cannot contain any other properties

52. Object Calisthenics
Rule 8: Use first class collections
‣ Objectives:
‣ Specific behaviors have a good place to stay
‣ Filtering, combining, mapping, ...

53. Object Calisthenics
Rule 8: Use first class collections
‣ DoctrineCommonCollectionsArrayCollection
‣ Countable
‣ IteratorAggregate (inherits Traversable)
‣ ArrayAccess

54. Object Calisthenics
Rule 9: Do not create getter/setter methods to properties
‣ Do not create getter/setter methods to properties

55. Object Calisthenics
Rule 9: Do not create getter/setter methods to properties
‣ Non-applicable to PHP due to language’s nature

56. Object Calisthenics
Rule 9: Do not create getter/setter methods to properties
/**
* THIS CLASS WAS GENERATED BY THE DOCTRINE ORM. DO NOT EDIT THIS FILE.
*/
class ApplicationCoreDomainUserModelUserProxy
! extends ApplicationCoreDomainUserModelUser
! implements DoctrineORMProxyProxy
{
// ...
public function getId()
{
$this->__load();
return parent::getId();
}
public function setId($id)
{
$this->__load();
return parent::setId($id);
}
// ...
}

57. Object Calisthenics
“Rule 10”: Document your code!
‣ Document your code!!!!!!!!!!!!!!!!!

58. Object Calisthenics
That’s all folks!
‣ Questions?
@guilhermeblanco
http://github.com/guilhermeblanco