PHP 访问者模式讲解和代码示例

<?php namespace RefactoringGuru\Visitor\RealWorld; /** * The Component interface declares a method of accepting visitor objects. * * In this method, a Concrete Component must call a specific Visitor's method * that has the same parameter type as that component. */ interface Entity { public function accept(Visitor $visitor): string; } /** * The Company Concrete Component. */ class Company implements Entity { private $name; /** * @var Department[] */ private $departments; public function __construct(string $name, array $departments) { $this->name = $name; $this->departments = $departments; } public function getName(): string { return $this->name; } public function getDepartments(): array { return $this->departments; } // ... public function accept(Visitor $visitor): string { // See, the Company component must call the visitCompany method. The // same principle applies to all components. return $visitor->visitCompany($this); } } /** * The Department Concrete Component. */ class Department implements Entity { private $name; /** * @var Employee[] */ private $employees; public function __construct(string $name, array $employees) { $this->name = $name; $this->employees = $employees; } public function getName(): string { return $this->name; } public function getEmployees(): array { return $this->employees; } public function getCost(): int { $cost = 0; foreach ($this->employees as $employee) { $cost += $employee->getSalary(); } return $cost; } // ... public function accept(Visitor $visitor): string { return $visitor->visitDepartment($this); } } /** * The Employee Concrete Component. */ class Employee implements Entity { private $name; private $position; private $salary; public function __construct(string $name, string $position, int $salary) { $this->name = $name; $this->position = $position; $this->salary = $salary; } public function getName(): string { return $this->name; } public function getPosition(): string { return $this->position; } public function getSalary(): int { return $this->salary; } // ... public function accept(Visitor $visitor): string { return $visitor->visitEmployee($this); } } /** * The Visitor interface declares a set of visiting methods for each of the * Concrete Component classes. */ interface Visitor { public function visitCompany(Company $company): string; public function visitDepartment(Department $department): string; public function visitEmployee(Employee $employee): string; } /** * The Concrete Visitor must provide implementations for every single class of * the Concrete Components. */ class SalaryReport implements Visitor { public function visitCompany(Company $company): string { $output = ""; $total = 0; foreach ($company->getDepartments() as $department) { $total += $department->getCost(); $output .= "\n--" . $this->visitDepartment($department); } $output = $company->getName() . " (" . money_format("%i", $total) . ")\n" . $output; return $output; } public function visitDepartment(Department $department): string { $output = ""; foreach ($department->getEmployees() as $employee) { $output .= " " . $this->visitEmployee($employee); } $output = $department->getName() . " (" . money_format("%i", $department->getCost()) . ")\n\n" . $output; return $output; } public function visitEmployee(Employee $employee): string { return money_format("%#6n", $employee->getSalary()) . " " . $employee->getName() . " (" . $employee->getPosition() . ")\n"; } } /** * The client code. */ $mobileDev = new Department("Mobile Development", [ new Employee("Albert Falmore", "designer", 100000), new Employee("Ali Halabay", "programmer", 100000), new Employee("Sarah Konor", "programmer", 90000), new Employee("Monica Ronaldino", "QA engineer", 31000), new Employee("James Smith", "QA engineer", 30000), ]); $techSupport = new Department("Tech Support", [ new Employee("Larry Ulbrecht", "supervisor", 70000), new Employee("Elton Pale", "operator", 30000), new Employee("Rajeet Kumar", "operator", 30000), new Employee("John Burnovsky", "operator", 34000), new Employee("Sergey Korolev", "operator", 35000), ]); $company = new Company("SuperStarDevelopment", [$mobileDev, $techSupport]); setlocale(LC_MONETARY, 'en_US'); $report = new SalaryReport(); echo "Client: I can print a report for a whole company:\n\n"; echo $company->accept($report); echo "\nClient: ...or for different entities " . "such as an employee, a department, or the whole company:\n\n"; $someEmployee = new Employee("Some employee", "operator", 35000); $differentEntities = [$someEmployee, $techSupport, $company]; foreach ($differentEntities as $entity) { echo $entity->accept($report) . "\r\n"; } // $export = new JSONExport();  // echo $company->accept($export); 

Client: I can print a report for a whole company: SuperStarDevelopment (USD550,000.00) --Mobile Development (USD351,000.00) $100,000.00 Albert Falmore (designer) $100,000.00 Ali Halabay (programmer) $ 90,000.00 Sarah Konor (programmer) $ 31,000.00 Monica Ronaldino (QA engineer) $ 30,000.00 James Smith (QA engineer) --Tech Support (USD199,000.00) $ 70,000.00 Larry Ulbrecht (supervisor) $ 30,000.00 Elton Pale (operator) $ 30,000.00 Rajeet Kumar (operator) $ 34,000.00 John Burnovsky (operator) $ 35,000.00 Sergey Korolev (operator) Client: ...or for different entities such as an employee, a department, or the whole company: 35000 Some employee (operator) Tech Support (199000) 70000 Larry Ulbrecht (supervisor) 30000 Elton Pale (operator) 30000 Rajeet Kumar (operator) 34000 John Burnovsky (operator) 35000 Sergey Korolev (operator) SuperStarDevelopment (550000) --Mobile Development (351000) 100000 Albert Falmore (designer) 100000 Ali Halabay (programmer) 90000 Sarah Konor (programmer) 31000 Monica Ronaldino (QA engineer) 30000 James Smith (QA engineer) --Tech Support (199000) 70000 Larry Ulbrecht (supervisor) 30000 Elton Pale (operator) 30000 Rajeet Kumar (operator) 34000 John Burnovsky (operator) 35000 Sergey Korolev (operator)