Object Calisthenics and Code Readability

Your code sucks,
let’s !x it!
Object Calisthenics and Code readability

Rafael Dohms

Rafael Dohms

photo credit: Eli White
@rdohms

Evangelist, Speaker and
Contributor.

Developer at WEBclusive.

Enabler at AmsterdamPHP.

Is it Readable?

Why does my
code suck?

Is it Readable?

Why does my
code suck?
Is it Testable?

Is it Maintainable? Is it Readable?

Why does my
code suck?
Is it Testable?

Is it Maintainable? Is it Readable?

Why does my
code suck?
Is it Reusable? Is it Testable?

<?php Does it look like this?
$list=mysql_connect("******","*******","*****");
if(!$list)echo 'Cannot login.';
else{
mysql_select_db("******", $list);
$best=array("0","0","0","0","0","0");
$id=mysql_num_rows(mysql_query("SELECT * FROM allnews"));
$count=0;
for($i=0;$i<6;$i++){
while(mysql_query("SELECT language FROM allnews WHERE id=$id-$count")!="he")$count+
+;
$best[$i]=mysql_query("SELECT id FROM allnews WHERE id=$id-$count");}
$id=$id-$count;
$maxdate=mktime(0,0,0,date('m'),date('d')-7,date('Y'));
while(mysql_query("SELECT date FROM allnews WHERE id=$id-$count")>=$maxdate){
if(mysql_query("SELECT language FROM allnews WHERE id=$id-$count")=="he"){
$small=$best[0];
while($i=0;$i<6;$i++){
if(mysql_query("SELECT score FROM allnews WHERE id=
$small)"<mysql_query("SELECT score FROM allnews WHERE id=$best[i+1]"))
$small=$best[i+1];}
$small")<mysql_query("SELECT score FROM allnews WHERE id=$id-$count")){
while($i=0;$i<6;$i++){
if($small==$best[i])$best[i]=mysql_query("SELECT id FROM
allnews WHERE id=$id-$count");}}}}
while($i=0;$i<6;$i++)
echo '<a href="news-page.php?id='.$best[i].'"><div class="box '.mysql_query("SELECT
type FROM allnews WHERE id=$best[i]").'">'.mysql_query("SELECT title FROM allnews WHERE id=
$best[i]").'<div class="img" style="background-image:url(images/'.mysql_query("SELECT
image1 FROM allnews WHERE id=$best[i]").');"></div></div></a>';
mysql_close($list);
}
?>

<?php Does it look like this?
$list=mysql_connect("******","*******","*****");
if(!$list)echo 'Cannot login.';
else{
mysql_select_db("******", $list);
$best=array("0","0","0","0","0","0");
$id=mysql_num_rows(mysql_query("SELECT * FROM allnews"));
$count=0;
for($i=0;$i<6;$i++){
while(mysql_query("SELECT language FROM allnews WHERE id=$id-$count")!="he")$count+
+;
$best[$i]=mysql_query("SELECT id FROM allnews WHERE id=$id-$count");}
$id=$id-$count;
$maxdate=mktime(0,0,0,date('m'),date('d')-7,date('Y'));
while(mysql_query("SELECT date FROM allnews WHERE id=$id-$count")>=$maxdate){
if(mysql_query("SELECT language FROM allnews WHERE id=$id-$count")=="he"){
$small=$best[0];
while($i=0;$i<6;$i++){
$small)"<mysql_query("SELECT score FROM allnews WHERE id=$best[i+1]"))
$small=$best[i+1];}
$small")<mysql_query("SELECT score FROM Rebecca WHERE id=$id-$count")){
If allnews Black was a developer
while($i=0;$i<6;$i++){
if($small==$best[i])$best[i]=mysql_query("SELECT id FROM
allnews WHERE id=$id-$count");}}}}
while($i=0;$i<6;$i++)
echo '<a href="news-page.php?id='.$best[i].'"><div class="box '.mysql_query("SELECT
type FROM allnews WHERE id=$best[i]").'">'.mysql_query("SELECT title FROM allnews WHERE id=
$best[i]").'<div class="img" style="background-image:url(images/'.mysql_query("SELECT
image1 FROM allnews WHERE id=$best[i]").');"></div></div></a>';
mysql_close($list);
}
?>

cal·is·then·ics - noun - /ˌkaləsˈTHeniks/
Calisthenics are a form of dynamic
exercise consisting of a variety of
simple, often rhythmical, movements,
generally using minimal equipment or
apparatus.

Object Calisthenics

cal·is·then·ics - noun - /ˌkaləsˈTHeniks/
Calisthenics are a form of dynamic
exercise consisting of a variety of
simple, often rhythmical, movements,
generally using minimal equipment or
apparatus.

Object Calisthenics
A variety of simple, often
rhythmical, exercises to achieve
better OO and code quality

“So here’s an exercise that can help you to internalize
principles of good object-oriented design and actually
use them in real life.”

-- Jeff Bay

Object Calisthenics

“So here’s an exercise that can help you to internalize
principles of good object-oriented design and actually
use them in real life.”

-- Jeff Bay

Object Calisthenics
Important:

PHP != JAVA

Adaptations will be done

Object Calisthenics
+
Readability Tips

“You need to write code that minimizes the time it would

Object Calisthenics
take someone else to understand it—even if that
someone else is you.”

+
-- Dustin Boswell and Trevor Foucher

Readability Tips

“You need to write code that minimizes the time it would

Object Calisthenics
take someone else to understand it—even if that
someone else is you.”

+
-- Dustin Boswell and Trevor Foucher

Readability Tips
I’m a tip

Disclaimer:
“These are guidelines, not rules”

OC #1
“Only one indentation
level per method”


'price',
'name',
'description',
'type',
);

$valid = true;

0 foreach ($products as $rawProduct) {

1 $fields = array_keys($rawProduct);

2 if (!in_array($requiredField, $fields)) {
3 $valid = false;
}
}
}

return $valid;
}


'price',
'name',
'description',
'type',
);

$valid = true;

$validationResult = validateSingleProduct($rawProduct, $requiredFields);

if ( ! $validationResult){
$valid = false;
}
}

return $valid;
}

function validateSingleProduct($product, $requiredFields)
{
$valid = true;


$valid = false;
}
}
return $valid;
}


'price',
'name',
'description',
'type',
);

$valid = true;

whitespace

$valid = false;
}
}

return $valid;
}

{
$valid = true;


$valid = false;
}
}
return $valid;
}


'price',
'name',
'description',
'type',
);

$valid = true;

whitespace

$valid = false;
}
}

return $valid;
}

{
$valid = true; duplicated logic

$valid = false;
}
}
return $valid;
}


'price',
'name',
'description',
'type',
);

$valid = true;

0 foreach ($products as
whitespace
$validationResult
$rawProduct) {
= validateSingleProduct($rawProduct, $requiredFields);

1 if ( ! $validationResult){

}
2 $valid = false;

}

return $valid;
}

{
$valid = true; duplicated logic

0 foreach(!in_array($requiredField, $fields))
($requiredFields as $requiredField) {

1 if {

} 2
$valid = false;

}
return $valid;
}


'price',
'name',
'description',
'type',
);

$valid = true;

0 foreach ($products as
$validationResult
$rawProduct) {
= validateSingleProduct($rawProduct, $requiredFields);

1 if ( ! $validationResult){

}
2 $valid = false;

}

return $valid;
}

{
$valid = true;


0 foreach(!in_array($requiredField, $fields))
($requiredFields as $requiredField) {

1 if {

} 2
$valid = false;

}
return $valid;
}


$requiredFields = array('price','name','description','type'); cheating!
I see
}

return true;
}

{

}


$requiredFields = array('price','name','description','type'); cheating!
I see
}

return true; Single line IF, simple operations
}

{

}



}

return true; Single line IF, simple operations return early
}

{

}



}

return true; Single line IF, simple operations return early
}

{

} C (native) functions are
faster then PHP

function validateProductList($products)
{
$validProducts = array_filter($products, 'isValidProduct');

return (count($products) == count($validProducts));
}

function isValidProduct($rawProduct)
{
$requiredFields = array('price', 'name', 'description', 'type');


}

function validateProductList($products) faster iteration
{

}

{


}

{

}

reusable method
{


}

{

}

reusable method
{


}

method name matches “true” result

{

}

assertable return: expected/returned
reusable method
{


}


List is more readable the plural

{

}

assertable return: expected/returned
reusable method
{


}


Key Benefits

• Single Responsibility Principle (S in SOLID)

• Increases re-use

OC #2
“Do not use the ‘else’
keyword”

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";
}

}

{


if ($form->isValid()){

if (!$repository->exists($entity) ) {
intermediate variable
} else {
$error = "Post Title already exists";
}
intermediate variable
} else {
$error = "Invalid fields";
}

}

{


if ( ! $form->isValid()){
return array('form' => $form, 'error' => 'Invalid fields');
}

if ($repository->exists($entity)){
return array('form' => $form, 'error' => 'Duplicate post title');
}



}

{

removed intermediates
}

}



}

{

}
early return
}



}

Separate code
into blocks.
{ Its like using
$repository = $this->getRepository('MyBundle:Post'); Paragraphs.
}
early return
}



}

Key Benefits

• Helps avoid code duplication
• Easier to read (single path)
• Reduces cyclomatic complexity

Ad
ap
OC #3

te
d
“Wrap primitive types
and strings, if there is
behaviour”

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

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

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

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

unclear operation

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

class Animate
{
public $animate;

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

}

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

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

class Animate
This can now encapsulate all
{
animation related operations
public $animate;

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

}

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

Key Benefits

• Type Hinting

• Encapsulation of operations

Ad
ap
OC #4

te
d
“Only one -> per line,
unless its getter or a
fluent interface”

Source: CodeIgniter

$this->base_url = $this->CI->config->site_url().'/'.$this->CI->uri->segment(1).$this-
>CI->uri->slash_segment(2, 'both');

$this->base_uri = $this->CI->uri->segment(1).$this->CI->uri->slash_segment(2, 'leading');

Source: CodeIgniter

properties are harder to mock


Source: CodeIgniter


no whitespace

Source: CodeIgniter


no whitespace

- Underlying encapsulation problem
- Hard to debug and test
- Hard to read and understand

Source: CodeIgniter


no whitespace

move everything to uri object

$this->getCI()->getUriBuilder()->getBaseUri(‘leading’);

- Underlying encapsulation problem
- Hard to debug and test
- Hard to read and understand

Source: Zend Framework App

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

Source: Symfony 2 Docs.


ﬂuent interface



ﬂuent interface

operator alignment



ﬂuent interface

operator alignment

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



ﬂuent interface

operator alignment

only getters (no operations)




ﬂuent interface

operator alignment



where did my
autocomplete go?



ﬂuent interface

operator alignment



where did my return null?
autocomplete go?


Key Benefits

• Readability
• Easier Mocking (Testing)

• Easier to Debug
• Demeter’s Law

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

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

} else {

if ($sy > $strSysMatImgH) {
}

if($nx > $strSysMatImgW) {
}
}

?
if($sx >= $sy) { ?
if ($sx > $strSysMatImgW) {
}
?
if ($ny > $strSysMatImgH) {
}

} else {

?
if ($sy > $strSysMatImgH) {
}

?
if($nx > $strSysMatImgW) {
}
}

Why do you abbreviate?

Its repeated many times,
and i’m lazy.


Its repeated many times,
and i’m lazy.
Underlying Problem!

You need to transfer those operations into a separate class.


function processResponseHeadersAndDefineOutput($response) { ... }



This method name is too long to type,
and i’m lazy.

more then one
responsibility?


This method name is too long to type,
and i’m lazy.

function getPage($data) { ... }

function startProcess() { ... }

$tr->process(“site.login”);

get from where?
function getPage($data) { ... }



get from where?
Use clearer names:
function getPage($data) { ... } fetchPage()
downloadPage()



get from where?
Use clearer names:
downloadPage()

Use a thesaurus:
fork, create, begin, open


get from where?
Use clearer names:
downloadPage()

Use a thesaurus:

Table row?


get from where?
Use clearer names:
downloadPage()

Use a thesaurus:

Table row?
Easy understanding, complete scope:
$translatorService

Key Benefits

• Clearer communication and maintainability

• Indicates underlying problems

Ad
ap
te
d
OC #6
“Keep your classes
small”

200 lines per class
10 methods per class
15 classes per package

Increased to include
docblocks

200 lines per class

docblocks 15-20 lines per method

200 lines per class

docblocks 15-20 lines per method

200 lines per class
read this as
namespace or folder

Key Benefits

• Single Responsibility
• Objective and clear methods

• Slimmer namespaces
• Avoids clunky folders

Ad
ap
OC #7

te
d
“Limit the number of
instance variables in a
class (max: 5)”

class MyRegistrationService
{

protected $userService;
protected $passwordService;
protected $logger;
protected $translator;
protected $entityManager;
protected $imageCropper;

// ...
}

{

protected $logger;
protected $translator;
protected $entityManager;
protected $imageCropper;

// ...
}

Limit: 5

{

protected $logger;
All DB interaction protected $translator;
should be in protected $entityManager;
userService protected $imageCropper; Use and event based
system and move this
// ... to listener
}

Limit: 5

Key Benefits

• Shorter dependency list

• Easier Mocking for unit test

OC #8
“Use first class
collections”

Doctrine:
ArrayCollection

$collection->getIterator();

$collection->filter(...);

$collection->append(...);

$collection->map(...);

Key Benefits

• Implements collection operations

• Uses SPL interfaces

Dr
op
pe
d
OC #9
“Do use accessors
(getter/setter)”

/**
* THIS CLASS WAS GENERATED BY THE DOCTRINE ORM. DO NOT EDIT THIS FILE.
*/
class DoctrineTestsModelsCMSCmsUserProxy
extends DoctrineTestsModelsCMSCmsUser
implements DoctrineORMProxyProxy
{

public function getId()
{
$this->__load();
return parent::getId();
}

public function getStatus()
{
$this->__load();
return parent::getStatus();
}

Property get/set syntax RFC may change the game.

/**
* THIS CLASS WAS GENERATED BY THE DOCTRINE ORM. DO NOT EDIT THIS FILE.
*/
class DoctrineTestsModelsCMSCmsUserProxy
extends DoctrineTestsModelsCMSCmsUser
implements DoctrineORMProxyProxy
{

public function getId()
{
$this->__load(); Example: Doctrine uses getters to
return parent::getId(); inject lazy loading operations
}

public function getStatus()
{
$this->__load();
return parent::getStatus();
}

Property get/set syntax RFC may change the game.

Key Benefits

• Injector operations

• Encapsulation of transformations

Cr
ea
te
d!
OC #10 (bonus!)
“Document your code!”

//check to see if the section above set the $overall_pref variable to void
if ($overall_pref == 'void')

// implode the revised array of selections in group three into a string
// variable so that it can be transferred to the database at the end of the
// page
$groupthree = implode($groupthree_array, "nr");

really?


// page

really?


// page

Documenting because i’m doing it wrong in an anusual way

$priority = isset($event['priority']) ? $event['priority'] : 0;

if (!isset($event['event'])) {
throw new InvalidArgumentException(...));
}

if (!isset($event['method'])) {
$event['method'] = 'on'.preg_replace(array(
'/(?<=b)[a-z]/ie',
'/[^a-z0-9]/i'
), array('strtoupper("0")', ''), $event['event']);
}

$definition->addMethodCall(
'addListenerService',
array($event['event'],
array($listenerId,
$event['method']),
$priority
));

Source: Symfony2


throw new InvalidArgumentException(...));
}

'/(?<=b)[a-z]/ie',
'/[^a-z0-9]/i'
}

array($listenerId, What does this do?
$event['method']),
$priority
));

Source: Symfony2

Add a simple comment:
throw new //Strips special chars and camel cases to onXxx
InvalidArgumentException(...));
}

'/(?<=b)[a-z]/ie',
'/[^a-z0-9]/i'
}

$event['method']),
$priority
));

Source: Symfony2

Add a simple comment:
throw new //Strips special chars and camel cases to onXxx
InvalidArgumentException(...));
}

Don’t explain bad
'/(?<=b)[a-z]/ie', code, ﬁx it!
'/[^a-z0-9]/i'
}

$event['method']),
$priority
));

Source: Symfony2

/**
* Checks whether an element is contained in the collection.
* This is an O(n) operation, where n is the size of the collection.
*
* @todo implement caching for better performance
* @param mixed $element The element to search for.
* @return boolean TRUE if the collection contains the element, or FALSE.
*/
function contains($element);

/**
*
*/

mark todo items so the
changes don’t get lost

A note on cost of
running function
/**
*
*/


Do a mind dump,
then clean it up.
A note on cost of
running function
/**
*
*/


Do a mind dump,
then clean it up.
A note on cost of
running function
/**
*
*/
Generate API docs
with phpDocumentor

Key Benefits

• Automatic API documentation
• Transmission of “line of thought”
• Avoids confusion

Recap
• #1 - Only one indentation level per method.

• #2 - Do not use the ‘else’ keyword.

• #3 - Wrap primitive types and string, if it has behavior.

• #4 - Only one -> per line, if not getter or fluent.

• #5 - Do not Abbreviate.

• #6 - Keep your classes small

• #7 - Limit the number of instance variables in a class (max: 5)

• #8 - Use first class collections

• #9 - Use accessors (getter/setter)

• #10 - Document your code!

Questions?

http://ﬁxthatcode.com

@rdohms

http://doh.ms http://joind.in/7404
http://slides.doh.ms

Recommended Links:

The ThoughtWorks Anthology
http://goo.gl/OcSNx

The Art of Readable Code
http://goo.gl/unrij

DISCLAIMER: This talk re-uses some of the examples used by Guilherme Blanco in his
original Object Calisthenic talk. These principles were studied and applied by us while we
worked together in previous jobs. The result taught us all a lesson we really want to spread
to other developers.

Object Calisthenics and Code Readability

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