Introduction to Object Oriented Programming in PHP

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Introduction to Object Oriented Programming in PHP @cocoders

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@cocoders Who Am I? Software Developer since 2007, beer lover, Founder of Cocoders

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What is Object Oriented Programming? @cocoders

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State(property) + Behavior(method) = Object Set of objects communicating each other = Object oriented program @cocoders

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employees[$employee->getTaxNumber()] = $employee; } } @cocoders

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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

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@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

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@cocoders Bertrand Meyer – creator of Eiffel (1986) Design by contract

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Communication is the key in OOP @cocoders

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How PHP can help you with communication and OOP? @cocoders

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Abstraction @cocoders

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Abstract classes @cocoders

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@cocoders namespace Cocoders\MedicalClinic; abstract class Employee { private $taxNumber; public function __construct($taxNumber) { $this->taxNumber = $taxNumber; } public function getTaxNumber() { return $this->taxNumber; } }

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@cocoders

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@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); } }

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employees[$employee->getTaxNumber()] = $employee; } } @cocoders

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@cocoders $clinic = new Clinic('ClinicId'); $clinic->hireEmployee(new Receptionist('911-11-11-111')); $clinic->hireEmployee(new Doctor( '911-11-10-111', 'AZG-11', ['neurologist'] ));

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Interfaces @cocoders

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@cocoders

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@cocoders employmentPositionList = $employmentPositionList; $this->clinicRegistry = $clinicRegistry; }

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@cocoders employmentPositionList->hireAtPosistion($command- >employmentPosistion, $command->employmentParameters); $clinic = $this->clinicRegistry->find($command->clinicId); $clinic->hireEmployee($employee); } }

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@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; } }

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@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'] ));

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@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'] ));

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WARNING: Premature abstraction @cocoders

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Plan your abstractions and extension points carefully! @cocoders

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Encapsulation – object should change state only in EXPECTED way @cocoders

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@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