Object Calisthenics Adapted for PHP
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Object Calisthenics Adapted for PHP

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The 9 "rules" of Object Calisthenics adapted for PHP development

The 9 "rules" of Object Calisthenics adapted for PHP development

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Object Calisthenics Adapted for PHP Object Calisthenics Adapted for PHP Presentation Transcript

  • Object Calisthenics Adapted for PHP
  • A little about me ● ● ● ● ● ● ● Bedford, VA Radford University 9+ Years PHP 8+ Years @ DE Hampton Roads PHP Comics Every Hulk Issue
  • Object Calisthenics ● ● ● ● ● ● First introduced by Jeff Bay Based on Java Development Guidelines Not Rules Difficulty varies Write Better Code Adapted for PHP
  • Object Calisthenics #1 “Only one level of indentation per method”
  • #1 Only one level of indentation public function validate(array $products) { $requiredFields = ['price', 'name', 'description']; $valid = true; foreach ($products as $rawProduct) { $fields = array_keys($rawProduct); foreach ($requiredFields as $requiredField) { if (!in_array($requiredField, $fields)) { $valid = false; } } } return $valid; }
  • #1 Only one level of indentation public function validate(array $products) { $requiredFields = ['price', 'name', 'description']; $valid = true; 0 foreach ($products as $rawProduct) { 1 $fields = array_keys($rawProduct); foreach ($requiredFields as $requiredField) { 2 if (!in_array($requiredField, $fields)) { 3 $valid = false; } } } return $valid; }
  • #1 Only one level of indentation public function validate(array $products) { $requiredFields = ['price', 'name', 'description']; $valid = true; foreach ($products as $rawProduct) { $valid = $valid && $this->validateSingle($rawProduct, $requiredFields); } return $valid; } public function validateSingle(array $product, array $requiredFields) { $fields = array_keys($product); return count(array_diff($requiredFields, $fields)) == 0; }
  • #1 Only one level of indentation Key Benefits ● Encourages Single Responsibility ● Increase Re-use
  • Object Calisthenics #2 “Do not use the ‘else’ keyword”
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } elseif (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } elseif (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } elseif (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { return early throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } elseif (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } if (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); reverse condition } if (is_string($exception)) { if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } else { throw new InvalidArgumentException('$exception was not a string, Exception or null'); }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } if (!is_string($exception)) { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } if (!is_string($exception)) { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } if ($exceptionArgs === null) { throw new Exception($exception); } else { if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); } } return early
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } if (!is_string($exception)) { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } if ($exceptionArgs === null) { throw new Exception($exception); } if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); }
  • #2 Do not use the ‘else’ keyword public function ensure($valueToEnsure, $valueToCheck, $exception = null, array $exceptionArgs = null) { if ($valueToEnsure === $valueToCheck) { return $valueToCheck; } if ($exception === null) { throw new Exception("'{$valueToEnsure}' did not equal '{$valueToCheck}'"); } if (!is_string($exception)) { throw new InvalidArgumentException('$exception was not a string, Exception or null'); } if ($exceptionArgs === null) { throw new Exception($exception); } if (array_key_exists($exception, self::$_exceptionAliases)) { $exception = self::$_exceptionAliases[$exception]; } $reflectionClass = new ReflectionClass($exception); throw $reflectionClass->newInstanceArgs($exceptionArgs); }
  • #2 Do not use the ‘else’ keyword Key Benefits ● Helps avoid code duplication ● Easier to read (single path) ● Reduces cyclomatic complexity
  • Object Calisthenics #3 “Wrap all primitives and Strings” *If there is behavior
  • #3 Wrap primitives and Strings class Item { final public static function find($id) { if (!is_string($id) || trim($id) == '') throw new InvalidArgumentException('$id must be a non-empty string'); // do find ... } final public static function create($id, array $data) { if (!is_string($id) || trim($id) == '') throw new InvalidArgumentException('$id must be a non-empty string'); // do create ... } }
  • #3 Wrap primitives and Strings class Item { final public static function find($id) { validation with id if (!is_string($id) || trim($id) == '') throw new InvalidArgumentException('$id must be a non-empty string'); // do find ... } final public static function create($id, array $data) validation with id { if (!is_string($id) || trim($id) == '') throw new InvalidArgumentException('$id must be a non-empty string'); // do create ... } }
  • #3 Wrap primitives and Strings class Id { private $value; final public function __construct($value) { if (!is_string($value) || trim($value) == '') throw new InvalidArgumentException('$value must be a non-empty string'); $this->value = $value; } final public function getValue() { return $this->value; } }
  • #3 Wrap primitives and Strings class Id { private $value; final public function __construct($value) validation encapsulated in constructor { if (!is_string($value) || trim($value) == '') throw new InvalidArgumentException('$value must be a non-empty string'); $this->value = $value; } final public function getValue() { return $this->value; } }
  • #3 Wrap primitives and Strings class Item { final public static function find(Id $id) { // do find ... } final public static function create(Id $id, array $data) { // do create ... } }
  • #3 Wrap primitives and Strings class Item { final public static function find(Id $id) { // do find ... } final public static function create(Id $id, array $data) { // do create ... } } $id now guaranteed to be valid.
  • #3 Wrap primitives and Strings Warning!!! Using large amounts of objects will increase the memory footprint of PHP.
  • #3 Wrap primitives and Strings Key Benefits ● Type Hinting ● Encapsulation of operations
  • Object Calisthenics #4 “Use first class collections”
  • #4 Use first class collections A class that contains a collection should contain no other instance variables.
  • #4 Use first class collections class Items implements Iterator { private $items = []; final public function add(Item $item) { // do add ... } final public function filter(array $filters) { // do filter ... } final public function merge(Items $items) { // do merge ... } }
  • #4 Use first class collections Key Benefits ● Implements collection operations ● Uses SPL interfaces ● Easier to merge collections and not worry about member behavior in them
  • Object Calisthenics #5 “One object operator per line”
  • #5 One object operator per line $this->manager->getConfig()->getSegment()->setName('foo');
  • #5 One object operator per line Properties are harder to mock $this->manager->getConfig()->getSegment()->setName('foo');
  • #5 One object operator per line Properties are harder to mock $this->manager->getConfig()->getSegment()->setName('foo'); Previous call could return null
  • #5 One object operator per line Properties are harder to mock May indicate feature envy $this->manager->getConfig()->getSegment()->setName('foo'); Previous call could return null
  • #5 One object operator per line Key Benefits ● Readability ● Easier Testing ● Easier to Debug
  • Object Calisthenics #6 “Do not abbreviate”
  • #6 Do not abbreviate public function getPage() { ... } public function startProcess() { ... } $smp->process("index");
  • #6 Do not abbreviate get what page from where? public function getPage() { ... } public function startProcess() { ... } $smp->process("index");
  • #6 Do not abbreviate get from where? public function getPage() { ... } public function startProcess() { ... } $smp->process("index"); ???
  • #6 Do not abbreviate get what page from where? public function getPage() { ... } Use clearer names: renderHomePage() downloadHomePage() public function startProcess() { ... } $smp->process("index"); ???
  • #6 Do not abbreviate get what page from where? public function getPage() { ... } Use clearer names: renderHomePage() downloadHomePage() public function startProcess() { ... } $smp->process("index"); ??? Use a thesaurus: fork, create, begin, open
  • #6 Do not abbreviate get what page from where? public function getPage() { ... } Use clearer names: renderHomePage() downloadHomePage() public function startProcess() { ... } $smp->process("index"); ??? Use a thesaurus: fork, create, begin, open Easy understanding, complete scope: $siteMapProcessor
  • #6 Do not abbreviate Key Benefits ● Clearer communication and maintainability ● Indicates underlying problems
  • Object Calisthenics #7 “Keep classes small”
  • #7 Keep classes small 200 lines per class (including docblocks) 10 methods per class 15 classes per namespace (folder)
  • #7 Keep classes small Key Benefits ● Single Responsibility ● Objective and clear methods ● Slimmer namespaces
  • Object Calisthenics #8 “Limit the number of instance variables in a class”
  • #8 Limit instance variables in a class class Client { private $_adapter; private $_cache; private $_logger; // ... } Limit: 2 - 5
  • #8 Limit instance variables in a class Key Benefits ● Shorter dependency list ● Easier Mocking for unit tests
  • Object Calisthenics #9 “Use getters/setters”
  • #9 Use Getters and Setters class Tally { public $total = 0; public function add($amount) { $this->total += $amount; } } $tally = new Tally(); $tally->add(1); // some other code ... $tally->total = -1; // some other code ... $tally->add(1); echo $tally->total . PHP_EOL;
  • #9 Use Getters and Setters class Tally { public $total = 0; public function add($amount) { $this->total += $amount } } $tally = new Tally(); $tally->add(1); // some other code ... $tally->total = -1 // some other code ... $tally->add(1); echo $tally->total . PHP_EOL; total can be changed without this instance knowing
  • #9 Use Getters and Setters class Tally { public $total = 0; public function add($amount) { $this->total += $amount } } $tally = new Tally(); total can be changed without this instance knowing $tally->add(1); // some other code ... $tally->total = -1 // some other code ... $tally->add(1); echo $tally->total . PHP_EOL; Causes unexpected results
  • #9 Use Getters and Setters class Tally total cannot be “reset” { private $total = 0; public function add($amount) { $this->total += $amount; } public function getTotal() { return $this->total; } } $tally = new Tally(); $tally->add(1); $tally->add(1); echo $tally->getTotal() . PHP_EOL; No unexpected results
  • #9 Use Getters and Setters Warning!!! Excessive setters and getters can be just as bad as public properties
  • #9 Use Getters and Setters Key Benefits ● Injector operations ● Encapsulation of transformations ● Encourages Open/Closed principle
  • Recap 1. 2. 3. 4. 5. 6. 7. 8. 9. One level of indentation per method Don’t use the else keyword Wrap primitives that have behavior Use first class collections One object operator per line Do not abbreviate Keep classes small Limit instance variables in a class Use Getters and setters
  • Object Calisthenics http://www.bennadel.com/resources/uploads/2012/ObjectCalisthenics.pdf @chadicus78 @hrphpmeetup Give us feedback at http://de12bcon.herokuapp.com/survey