Now you gonna put your code to do some push ups and pull ups, let's see how much your code can do!
Object Calisthenics provides invaluable guidelines for writing maintainable and comprehensible code. Let's explore each guideline within the context of PHP 8 to understand how they contribute to code quality and readability.
The guidelines
- Use only one level of indentation per method.
- Don’t use the else keyword.
- Wrap all primitives and strings.
- Use only one dot per line.
- Don’t abbreviate.
- Keep all entities small.
- Don’t use any classes with more than two instance variables.
- Use first-class collections.
- Don’t use any getters/setters/properties.
1. Use only one level of indentation per method.
it keeps more readable and helpful to understand what is happening, use the extract method stategy to achive that.
# Other
function moreIdentationFunction()
{
$counter = [];
for ($i = 0; $i < 10; $i++) { # level zero
$counter[] = $i;
foreach ($counter as $value) { # level one
if ($value == 5) { # level two
continue;
}
$counter[$value] = $value . ' result';
}
}
}
# Guideline
function lessIdentationFunction()
{
$counter = [];
for ($i = 0; $i < 10; $i++) { # level zero
$counter[] = $i;
$counter = generateResult($counter);
}
}
function generateResult($counter)
{
foreach ($counter as $value) { # level zero
if ($value == 5) { # level one
continue;
}
$counter[$value] = $value . ' result';
}
return $counter;
}
2. Don’t use the else keyword.
Most of cases you could avoid the else keyword when you adapt your algorithm.
function dontUseElse($age)
{
# Other
if ($age < 18) {
echo 'Under 18';
} else {
echo 'Over 18';
}
# Guideline
if ($age < 18) {
echo 'Under 18';
}
echo 'Over 18';
}
3. Wrap all primitives and strings.
Creating a class that encapsulates and provides a consistent interface for working with primitive values and strings.
class WrapAllPrimitives
{
private $value;
public function __construct($value)
{
if (!is_string($value) || !is_numeric($value) || !is_bool($value)) {
throw new InvalidArgumentException('Value must be a string, number or boolean');
}
$this->value = $value;
}
public function getValue()
{
return $this->value;
}
}
$stringWrapper = new WrapAllPrimitives('Hello, world!');
echo $stringWrapper->getValue(); // Outputs: Hello, world!
$numberWrapper = new WrapAllPrimitives(42);
echo $numberWrapper->getValue(); // Outputs: 42
$boolWrapper = new WrapAllPrimitives(true);
echo $boolWrapper->getValue(); // Outputs: 1
4. Use only one dot per line
Avoid the break of the open closed principle and also avoid mysterious exceptions but don't aplly in fluent API, also is more easy to see on the debug stacktrace.
# Other
class PersonOther
{
private $name;
public function __construct(string $name)
{
$this->name = $name;
}
public function getName(): string|object
{
return $this->name;
}
public function getFormattedName(): string|object
{
return strtoupper($this->name);
}
}
$personOther = new PersonOther('Charlie');
// Bad Example: Chained method calls with multiple dots in one line
$personOther->getName()->getFormattedName();
# Guideline
class PersonGuideline
{
private $name;
public function __construct(string $name)
{
$this->name = $name;
}
public function getName(): string
{
return $this->name;
}
}
class CarGuideline
{
private $owner;
public function __construct(PersonGuideline $owner)
{
$this->owner = $owner;
}
public function getOwnerName(): string
{
return $this->owner->getName();
}
}
$personGuideline = new PersonGuideline('Alice');
$carGuideline = new CarGuideline($personGuideline);
$carGuideline->getOwnerName();
5. Don’t abbreviate.
Explain what the method or the variable means, avoid redundant names on class methods.
# Other
$cpm = 199;
class UserOther
{
# people know the Add is for user, it is redundant.
function AddUser()
{
}
function DeleteUser()
{
}
}
# Guideline
$costsPerMill = 199;
class UserGuideline
{
# Keep the context
function Add()
{
}
function Delete()
{
}
}
6. Keep all entities small.
Keep classes with 50 lines of code, doing that it shows your class is doing only one thing.
class FiftyLinesClass
{
public function __construct()
{
throw new Exception('50 shades of code');
}
}
7. Don’t use any classes with more than two instance variables.
Your constructor should have only two injections not more than that also applies to local instances inside the class.
# Other
class TooMuchVariables
{
public function __construct(
private array $data1,
private array $data2,
private array $data3,
private array $data4
) {
}
}
# Guideline
class OnlyTwoVariables
{
public function __construct(
private array $data1,
private array $data2
) {
}
}
8. Use first-class collections.
Encapsulate your dataset to avoid misusing of the values or actions that could happen, avoid breaking of business rules as well and directly manipulation of the instance.
# Other
class ClientCollectionOther
{
private array $clientsData;
public function __construct()
{
$this->clientsData = [
1 => 'Morfeu',
2 => 'Neo'
];
}
function get($id)
{
return $this->clientsData[$id];
}
function add(string $name)
{
return array_push($this->clientsData, $name);
}
}
class RenderClientOther
{
public function __construct(public ClientCollectionOther $clients)
{
}
function show($id)
{
echo $this->clients->get($id);
}
function insert($name)
{
echo $this->clients->add($name);
}
}
$render = new RenderClientOther((new ClientCollectionOther));
$render->show(2);
$render->insert('Trinity');
$render->show(3);
# Guideline
class ClientCollectionGuideline
{
private array $clients;
public function __construct()
{
$this->clients = [];
}
public function addClient(string $name): void
{
$this->clients[] = $name;
}
public function getClientById(int $id): ?string
{
return $this->clients[$id] ?? null;
}
public function getAllClients(): array
{
return $this->clients;
}
}
class RenderClientGuideline
{
private ClientCollectionGuideline $clients;
public function __construct(ClientCollectionGuideline $clients)
{
$this->clients = $clients;
}
public function showClientById(int $id): void
{
$client = $this->clients->getClientById($id);
if ($client !== null) {
echo $client;
}
}
public function insertClient(string $name): void
{
$this->clients->addClient($name);
}
}
$clients = new ClientCollectionGuideline();
$clients->addClient('Morfeu');
$clients->addClient('Neo');
$render = new RenderClientGuideline($clients);
$render->showClientById(1);
$render->insertClient('Trinity');
$render->showClientById(2);
9. Don’t use any getters/setters/properties.
Use methods to do the actions for you instead of the set or get methods.
# Other
class WithGetAndSet
{
private int $score;
public function __construct(int $score)
{
$this->score = $score;
}
public function getScore(): int
{
return $this->score;
}
public function setScore(int $score): void
{
$this->score = $score;
}
public function increase(): int
{
$this->score += 2;
return $this->score;
}
public function decrease(): int
{
$this->score -= 2;
return $this->score;
}
}
# Guideline
class WithouttGetAndSet
{
private int $score;
public function __construct(int $score)
{
$this->score = $score;
}
public function increase(): int
{
$this->score += 2;
return $this->score;
}
public function decrease(): int
{
$this->score -= 2;
return $this->score;
}
}
Those guidelines are good to give us directions on how to code better and more cleaner, in my opinion coding is something that needs to be empathy, following some of those guidelines help others and yourself to understand your code better.
However you need to think about which one to follow I guess some are too much and drives to more complexity or even only a unnecessary rabbit hole.
On the other hand some are natural and easy to apply and with the time comes natural and specially because you see a lot of people using it.