PHP 状态模式讲解和代码示例

<?php namespace RefactoringGuru\State\Conceptual; /** * The Context defines the interface of interest to clients. It also maintains a * reference to an instance of a State subclass, which represents the current * state of the Context. */ class Context { /** * @var State A reference to the current state of the Context. */ private $state; public function __construct(State $state) { $this->transitionTo($state); } /** * The Context allows changing the State object at runtime. */ public function transitionTo(State $state): void { echo "Context: Transition to " . get_class($state) . ".\n"; $this->state = $state; $this->state->setContext($this); } /** * The Context delegates part of its behavior to the current State object. */ public function request1(): void { $this->state->handle1(); } public function request2(): void { $this->state->handle2(); } } /** * The base State class declares methods that all Concrete State should * implement and also provides a backreference to the Context object, associated * with the State. This backreference can be used by States to transition the * Context to another State. */ abstract class State { /** * @var Context */ protected $context; public function setContext(Context $context) { $this->context = $context; } abstract public function handle1(): void; abstract public function handle2(): void; } /** * Concrete States implement various behaviors, associated with a state of the * Context. */ class ConcreteStateA extends State { public function handle1(): void { echo "ConcreteStateA handles request1.\n"; echo "ConcreteStateA wants to change the state of the context.\n"; $this->context->transitionTo(new ConcreteStateB()); } public function handle2(): void { echo "ConcreteStateA handles request2.\n"; } } class ConcreteStateB extends State { public function handle1(): void { echo "ConcreteStateB handles request1.\n"; } public function handle2(): void { echo "ConcreteStateB handles request2.\n"; echo "ConcreteStateB wants to change the state of the context.\n"; $this->context->transitionTo(new ConcreteStateA()); } } /** * The client code. */ $context = new Context(new ConcreteStateA()); $context->request1(); $context->request2(); 

Context: Transition to RefactoringGuru\State\Conceptual\ConcreteStateA. ConcreteStateA handles request1. ConcreteStateA wants to change the state of the context. Context: Transition to RefactoringGuru\State\Conceptual\ConcreteStateB. ConcreteStateB handles request2. ConcreteStateB wants to change the state of the context. Context: Transition to RefactoringGuru\State\Conceptual\ConcreteStateA.