策略模式,什麼是策略模式,定義了算法族,分別封裝起來,讓他們之間能夠相互替換,此模式讓算法的變化獨立於使用算法的客戶。php
下面咱們就用鴨子來詮釋一下策略模式,鴨子有兩種行爲呱呱叫和飛,可是並非全部的鴨子都會呱呱叫和飛,因此咱們把這兩個賦予變化的行爲提取出來。算法
<?php abstract class Duck{ public $flyBehavior; public $quackBehavior; public function __construct(){ } public function performFly(){ $this->flyBehavior->fly(); } public function performQuack(){ $this->quackBehavior->quack(); } public function setFlyBehavior(FlyBehavior $fb){ $this->flyBehavior = $fb; } public function setQuackBehavior(QuackBehavior $qb){ $this->quackBehavior = $qb; } public function swim(){ } abstract function display(); } interface FlyBehavior{ public function fly(); } class FlywithWings implements FlyBehavior{ public function fly(){ echo "i'm flying!\n"; } } class FlyNoWay implements FlyBehavior{ public function fly(){ echo "i can't fly.\n"; } } class FlyRocketPowered implements FlyBehavior{ public function fly(){ echo "i'm flying with a rocket!\n"; } } interface QuackBehavior{ public function quack(); } class Quack implements QuackBehavior{ public function quack(){ echo "quack!\n"; } } class MuteQuack implements QuackBehavior{ public function quack(){ echo "silence\n"; } } class MallardDuck extends Duck{ public function __construct(){ $this->quackBehavior = new Quack(); $this->flyBehavior = new FlyNoWay(); } public function display(){ echo "i'm a real mallar duck\n"; } } $duck = new MallardDuck; $duck->performFly(); $duck->setFlyBehavior(new FlyRocketPowered); $duck->performFly(); ?>
從上面的代碼能夠看出咱們把鴨子抽象出來,而飛行行爲和呱呱叫行車以接口的形式,設計的原則是多用組合,少用繼承,用上面的寫法,相對彈性大點,不只將算法封裝成類,更能夠「在運行時動態的改變行爲」,只要組合行爲對象符合正確的接口標準便可。this