Object Calisthenics Applied to PHP

Object Calisthenics
Applied to PHP

Object Calisthenics
The speaker

@guilhermeblanco

http://github.com/guilhermeblanco

Object Calisthenics
Agenda

‣ Motivation
‣ Rules
‣ Application

Object Calisthenics
Erm... WTH is Object Calisthenics?

‣ Object Calisthenics

Object Calisthenics

‣ Object Calisthenics

Term derived from greek,
“exercise”, under the
context of gymnastics.

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

Object Calisthenics
Motivation

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

Object Calisthenics
Rules

‣ Nine (9) rules “very” simple...

Object Calisthenics
Rule 1: Only one indentation level per method

‣ Only one indentation level per method

Object Calisthenics
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 {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}

return $input;
}

Object Calisthenics
public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;


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!",
);
} else {
);
}
}
}
}

return $input;
}

Object Calisthenics
public function validateForm($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;


if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}

if (strpos($message, "empty")) {
"The field {$field} cannot be empty!",
);
} else {
);
}
}
}
}

Object Calisthenics
{
$data = $_POST;


return $input;
}

1 foreach(strpos($message, "empty")) {
($messageList as $message) {
2 if throw new Tss_FormException(
3 "The field {$field} cannot be empty!",
);
} else {
);
}
}
}
}

Object Calisthenics
{
$data = $_POST;


return $input;
}

$errorMessage = (strpos($message, "empty") === false)
? "The field {$field} cannot be empty!"
: "{$message}";

$errorMessage, 3, 'javascript:history.back();'
);
}
}
}

Object Calisthenics
{
$data = $_POST;


return $input;
}

1 foreach ($messageList as $message) { "empty") === false)
2 $errorMessage = (strpos($message,be empty!"
? "The field {$field} cannot
: "{$message}";

);
}
}
}

Object Calisthenics
public function validatePost($filters = array(), $validators = array(), $options = null)
{
$data = $_POST;


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}";

);
}
}

Object Calisthenics
Rule 2: Do not use the “else” keyword

‣ Never use the “else” keyword

Object Calisthenics
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');
}
}

Object Calisthenics
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);
}

Object Calisthenics
Rule 3: Wrap primitive types and strings

‣ Wrap all primitive types and strings

Object Calisthenics

‣ 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

Object Calisthenics

‣ But... if the variable of primitive type has a behavior, it
must be encapsulated

Object Calisthenics
class UIComponent
{
! // ...
!
public function repaint($animate = true)
{
// ...
}
}

// ...
$component->repaint(false);

Object Calisthenics
class UIComponent
{
! // ...
!
public function repaint(Animate $animate)
{
// ...
}
}

class Animate
{
public $animate;

public function __construct($animate = true)
{
$this->animate = $animate;
}
}

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

Object Calisthenics
Rule 4: Only one dot per line

‣ Only one dot (arrow for PHP) per line

Object Calisthenics

‣ Not applicable to PHP...

Object Calisthenics

‣ ...but multiple nested calls...
‣ tend to expose an encapsulation problem
‣ increase difﬁculty to debug and exception handling
‣ do not represent an atomic action

Object Calisthenics

‣ We could adapt to the language, contemplating...

Object Calisthenics

‣ A chain of different objects, but only if the execution
only includes getters and setters

$user->getLocationPoint()->getCountry()->getName();

Object Calisthenics

‣ A chain of a unique object, through the usage of a
ﬂuent interface

$filterChain->addFilter(new Zend_Filter_Alpha())
->addFilter(new Zend_Filter_StringToLower());

Object Calisthenics
Rule 5: Do not abbreviate

‣ Do not abbreviate

Object Calisthenics

Object Calisthenics

‣ Think about it... why do you want to abbreviate?

Object Calisthenics

‣ Write the same name repeatedly?

Object Calisthenics

‣ Then your method is reused multiple times,
signalling a code duplication.

Object Calisthenics

‣ Method name too long?

Object Calisthenics

‣ Method name too long?
‣ Maybe your class has multiple responsibilities or it
is missing a helper class (bad architecture).

Object Calisthenics
Rule 6: Keep your entities small

‣ Keep your entities small

Object Calisthenics

‣ Original rule: 50 lines per class

Object Calisthenics

‣ 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.

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

‣ Do not create classes with more than 2 instance
variables

Object Calisthenics

‣ Objective:
‣ Low cohesion
‣ Better encapsulation

Object Calisthenics

‣ The original rule points to 2 instance variables
‣ To PHP, the suggestion is no more than 5 variables

Object Calisthenics
Rule 8: Use ﬁrst class collections

‣ Use ﬁrst class collections

Object Calisthenics

‣ The rule is simple: Any class that contains a collection
(array to PHP), cannot contain any other properties

Object Calisthenics

‣ Objectives:
‣ Speciﬁc behaviors have a good place to stay
‣ Filtering, combining, mapping, ...

Object Calisthenics

‣ DoctrineCommonCollectionsArrayCollection
‣ Countable
‣ IteratorAggregate (inherits Traversable)
‣ ArrayAccess

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

‣ Do not create getter/setter methods to properties

Object Calisthenics

‣ Non-applicable to PHP due to language’s nature

Object Calisthenics
/**
* 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);
}

// ...
}

Object Calisthenics
“Rule 10”: Document your code!

‣ Document your code!!!!!!!!!!!!!!!!!

Object Calisthenics
That’s all folks!

‣ Questions?

@guilhermeblanco

http://github.com/guilhermeblanco

Object Calisthenics Applied to PHP

In this document