1st CI&T Lightning Talks: Writing better code with Object Calisthenics

Writing better
code with
Object Calisthenics
Lucas Arruda
lucas@ciandt.com
github.com/larruda
Adapted from Jeff Bay’s paper from
“The ThoughtWorks Anthology”
and Guilherme Blanco’s presentation.

7 code qualities
cohesion
loose coupling
no redundancy
encapsulation
testability
readability
focus

1. One level of indentation per method
class Board {
...
String board() {
StringBuffer buf = new StringBuffer();
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 10; j++)
buf.append(data[i][j]);
buf.append(“n”);
}
return buf.toString();
}
}

class Board {
...
String Board() {
collectRows(buf);
}
void collectRows(StringBuffer buf) {
for (int i = 0; i < 10; i++)
collectRow(buf, i);
}
void collectRow(StringBuffer buf, int row) {
for (int i = 0; i < 10; i++)
Buf.append(data[row][i]);
buf.append(“n”);
}
}

public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ($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;
}

public function validateForm($filters='', $validators='', $options='')
{
$data = $_POST;
$input = new Zend_Filter_Input($filters, $validators, $data);
$input->setDefaultEscapeFilter(new Zend_Filter_StringTrim());
if ( ! ($input->hasInvalid() || $input->hasMissing())) {
return $input;
}
if (strpos($message, "empty")) {
"The field {$field} cannot be empty!",
3, 'javascript:history.back();'
);
} else {
"{$message}", 3, 'javascript:history.back();'
);
}
}
}
}

public function validateForm($filters='', $validators='', ...
{
$data = $_POST;
$input = new Zend_Filter_Input ($filters, $validators, $data);
$input->setDefaultEscapeFilter( new Zend_Filter_StringTrim ());
return $input;
}
$errorMessage = (strpos($message, "empty") === false)
? "The field {$field} cannot be empty!"
: "{$message}";
throw new Tss_FormException (
$errorMessage, 3, 'javascript:history.back();'
);
}
}
}

public function validateForm($filters='', $validators='', ...
{
$data = $_POST;
$input = new Zend_Filter_Input ($filters, $validators, $data);
$input->setDefaultEscapeFilter( new Zend_Filter_StringTrim ());
return $input;
}
$messageKey = key($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();'
);
}
}

2. Don’t use the ELSE keyword
if (status == DONE) {
doSomething();
} else {
…
}

class Board {
...
String board(StringBuffer buf) {
if (buf.length()) {
}
else {
collectRows(buf);
}
}
...
}

class Board {
...
String board(StringBuffer buf) {
if (!buf.length()) {
collectRows(buf);
}
}
...
}

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);
}

3. Wrap all primitives and Strings

If the primitive type has a behavior it
should be encapsulated

class UIComponent
{
// ...
public function repaint($animate = true)
{
// …
}
// ...
$component->repaint(false);
}

class UIComponent
{
// ...
public function repaint(Animate $animate)
{
// ...
}
}
class Animate
{
public $animate;
public function __construct($animate = true)
{
$this->animate = $animate;
}
}
// ...
$component->repaint(new Animate(false));

4. First class collections
Any class that contains a collection/array
should not contain any other member
variables
Java Collections follow this rule

4. First class collections
Transversable
Countable
Iterator
Filtering
Mapping
Combining

5. One dot/arrow per line
Sign of misplaced responsibilities
The Law of Demeter
“Only talk to your friends”

class Board {
...
class Piece {
...
String representation;
}
class Location {
...
Piece current;
}
String boardRepresentation () {
for (Location l: squares())
buf .append(l.current.representation .substring(0,
1));
}
}

class Board {
...
class Piece {
...
private String representation;
String character() {
return representation.substring(0, 1);
}
void addTo(StringBuffer buf) {
buf.append(character());
}
}
class Location {
...
private Piece current;
void addTo(StringBuffer buf) {
current.addTo(buf);
}
}
String boardRepresentation() {
for (Location l: squares())
l.addTo(buf);
}
}

6. Don’t abbreviate
Are you writing the same name repeatedly?
method being used multiple times
sign of code duplication
Is the method name too long?
class with multiple responsibilities
missing additional class
redundancy

7. Keep all entities small
Java
No class over 50 lines
No packages over 10 files
PHP
No class over 100 lines
No packages over 15 files
Packages, like classes, should be
cohesive and have a purpose

8. No classes with more than two/five instance variables
Improve cohesion
Split on more entities

9. No getters/setters/properties
Improve encapsulation
“Tell, don’t ask”

Q&A
ciandt.com
http://www.cs.helsinki.fi/u/luontola/tdd-2009/ext/ObjectCalisthenics.pdf
http://www.slideshare.net/guilhermeblanco/object-calisthenics-applied-to-php
https://www.youtube.com/watch?v=ftBUHrxfOcc

ciandt.com
lunascar@gmail.com
@lunascarruda
google.com/+LucasArruda
fb.com/lucasnarruda
linkedin.com/in/larruda
github.com/larruda
coderbits.com/larruda
drupal.org/user/1009514

1st CI&T Lightning Talks: Writing better code with Object Calisthenics

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