PHP设计模式 - 策略模式

<?phpinterface Strategy { // 抽象策略角色，以接口实现 ???public function do_method(); // 算法接口}class ConcreteStrategyA implements Strategy { // 具体策略角色A ????public function do_method() { ???????echo ‘do method A‘; ???}}class ConcreteStrategyB implements Strategy { // 具体策略角色B ????public function do_method() { ???????echo ‘do method B‘; ???}}class ConcreteStrategyC implements Strategy { // 具体策略角色C ???public function do_method() { ???????echo ‘do method C‘; ???}}class Question{ // 环境角色 ???private $_strategy; ???public function __construct(Strategy $strategy) { ???????$this->_strategy = $strategy; ???} ????public function handle_question() { ???????$this->_strategy->do_method(); ???}}// client$strategyA = new ConcreteStrategyA();$question = new Question($strategyA);$question->handle_question();//输出do method A$strategyB = new ConcreteStrategyB();$question = new Question($strategyB);$question->handle_question();//输出do method B$strategyC = new ConcreteStrategyC();$question = new Question($strategyC);$question->handle_question();//输出do method C