Introduction to Object Oriented Programming in PHP

Powiemy sobie o podstawowych strukturach, elementach języka oraz wzorcach związanych z programowaniem obiektowym w PHP. Zahaczymy o polimorfizm, abstrakcję, hermetyzację oraz o zasady SOLID

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1. Introduction to Object Oriented Programming in PHP @cocoders
2. @cocoders Who Am I? Software Developer since 2007, beer lover, Founder of Cocoders
3. What is Object Oriented Programming? @cocoders
4. State(property) + Behavior(method) = Object Set of objects communicating each other = Object oriented program @cocoders
5. <?php namespace Cocoders\MedicalClinic; class Clinic { /** * @var Employee[] */ private $employees = []; public function hireEmployee(Employee $employee) { $this->employees[$employee->getTaxNumber()] = $employee; } } @cocoders
6. class Clinic { /** * @var PatientCase[] */ private $patientCases = []; //.. public function registerPatient(Patient $patient, $hasInsurance) { if ($case = $this->findPatientCase($patient->getIdNumber())) { $case->registerVisit($patient, $hasInsurance); return; } $this->patientCases[$patient->getIdNumber()] = new PatientCase($patient, $hasInsurance); } } @cocoders
7. @cocoders Alan Kay – creator of Smalltalk (1998) Smalltalk is not only NOT its syntax or the class library, it is not even about classes. The big idea is "messaging" - that is what the kernel of Smalltalk/Squeak is all about
8. @cocoders Bertrand Meyer – creator of Eiffel (1986) Design by contract
9. Communication is the key in OOP @cocoders
10. How PHP can help you with communication and OOP? @cocoders
11. Abstraction @cocoders
12. Abstract classes @cocoders
13. @cocoders namespace Cocoders\MedicalClinic; abstract class Employee { private $taxNumber; public function __construct($taxNumber) { $this->taxNumber = $taxNumber; } public function getTaxNumber() { return $this->taxNumber; } }
14. @cocoders <?php namespace Cocoders\MedicalClinic\Employee; use Cocoders\MedicalClinic\Employee; class Receptionist extends Employee { }
15. @cocoders namespace Cocoders\MedicalClinic\Employee; use Cocoders\MedicalClinic\Employee; class Doctor extends Employee { private $licenseNumber; private $specializations = []; public function __construct($taxNumber, $licenseNumber, $specializaitons) { parent::__construct($taxNumber); $this->licenseNumber = $licenseNumber; $this->specializations = $specializaitons; } public function hasSpecialization($specialization) { return false !== array_search($specialization, $this->specializations, true); } }
16. <?php namespace Cocoders\MedicalClinic; class Clinic { /** * @var Employee[] */ private $employees = []; public function hireEmployee(Employee $employee) { $this->employees[$employee->getTaxNumber()] = $employee; } } @cocoders
17. @cocoders $clinic = new Clinic('ClinicId'); $clinic->hireEmployee(new Receptionist('911-11-11-111')); $clinic->hireEmployee(new Doctor( '911-11-10-111', 'AZG-11', ['neurologist'] ));
18. Interfaces @cocoders
19. @cocoders <?php namespace Cocoders\MedicalClinic; interface ClinicRegistry { /** * @param $id * @return Clinic */ public function find($id); public function add(Clinic $clinic); }
20. @cocoders <?php namespace Cocoders\MedicalClinic\UseCase; use Cocoders\MedicalClinic\ClinicRegistry; use Cocoders\MedicalClinic\Employee\EmploymentPositionList; final class HireEmployee { private $employmentPositionList; private $clinicRegistry; public function __construct( EmploymentPositionList $employmentPositionList, ClinicRegistry $clinicRegistry ) { $this->employmentPositionList = $employmentPositionList; $this->clinicRegistry = $clinicRegistry; }
21. @cocoders <?php namespace Cocoders\MedicalClinic\UseCase; use Cocoders\MedicalClinic\ClinicRegistry; use Cocoders\MedicalClinic\Employee\EmploymentPositionList; final class HireEmployee { //previous slide public function execute(HireEmployee\Command $command) { $employee = $this->employmentPositionList->hireAtPosistion($command- >employmentPosistion, $command->employmentParameters); $clinic = $this->clinicRegistry->find($command->clinicId); $clinic->hireEmployee($employee); } }
22. @cocoders namespace Cocoders\InMemoryAdapter\MedicalClinic; use Cocoders\MedicalClinic\Clinic; use Cocoders\MedicalClinic\ClinicRegistry as ClinicRegistryInterface; final class ClinicRegistry implements ClinicRegistryInterface { private $clinics = []; /** * @param $taxIdNumber * @return Clinic */ public function find($id) { if (isset($this->clinics[$id])) { return $this->clinics[$id]; } } public function add(Clinic $clinic) { if ($this->find($clinic->getId())) { return; } $this->clinics[$clinic->getId()] = $clinic; } }
23. @cocoders $clinicRegistry = new \Cocoders\InMemoryAdapter\ClinicRegistry(); $clinicRegistry->add(new Clinic(1)); $hireEmployee = new HireEmployee( new EmploymentPositionList(), $clinicRegistry ); $hireEmployee->execute(new \Cocoders\MedicalClinic\UseCase\HireEmployee\Command( $clinicId = 1, $position = 'receptionist', $parameters = ['911-11-10-111'] ));
24. @cocoders $clinicRegistry = new \Cocoders\MysqlAdapter\ClinicRegistry($connection); $clinicRegistry->add(new Clinic(1)); $hireEmployee = new HireEmployee( new EmploymentPositionList(), $clinicRegistry ); $hireEmployee->execute(new \Cocoders\MedicalClinic\UseCase\HireEmployee\Command( $clinicId = 1, $position = 'receptionist', $parameters = ['911-11-10-111'] ));
25. WARNING: Premature abstraction @cocoders
26. Plan your abstractions and extension points carefully! @cocoders
27. Encapsulation – object should change state only in EXPECTED way @cocoders
28. @cocoders $clinic->setTaxIdNumber('9562307984'); $clinic->setName('Cocoders'); $clinic->addEmployee((new Employee())- >setFirstName('Leszek'))); $clinic->getEmployees()->add((new Employee())->setFirstName('Szymon')); vs $clinic = new Clinic('Cocoders', ' 9562307984'); $clinic->hire(new Candidate('Leszek')); $clinic->hire(new Candidate('Szymon')); Violation of encapulation
29. Encapsulation allows to control communication in our OO program @cocoders
30. How to design our objects? @cocoders
31. SOLID @cocoders
32. Cohesion & Coupling @cocoders
33. Law of Demeter @cocoders
34. Thank You! @cocoders
35. Questions? @cocoders