面向对象的PHP与关键字接口，扩展，实现

Question

在过去的几个月中，我学习纯粹的操作系统已经走过了很长的路，现在我正在将设计模式应用到我的工作中！所以我不得不扩展我的php知识，并且我正在使用接口，扩展它们，然后实现这些接口的类。我的问题是有关从延伸另一个借此代码实例的接口构造类：

interface Car 
{ 
    function doGeneralCarStuff(); 
    vinNumber =; 
} 

interface CompactCar extends Car 
{ 
    static $numCompactCars; 
    function doCompactCarStuff(); 
} 

class HondaCivic implements CompactCar 
{ 
    function doGeneralCarStuff() 
    { 
    //honk horn , blink blinkers, wipers on, yadda yadda 
    } 

    function doCompactCarStuff() 
    { 
     //foo and bar and foobar 
    } 

} 

class ToyotaCorolla implements CompactCar 
{ 
    function doGeneralCarStuff() 
    { 
    //honk horn , blink blinkers, wipers on, yadda yadda 
    } 

    function doCompactCarStuff() 
    { 
     //foo and bar and foobar 
    } 

} 


myCar = new HondaCivic(); 
myFriendCar = new ToyotaCorolla(); 

好了，现在可以说，我想知道的东西从我的本田延伸即CompactCar接口接口的约一。我想知道有多少小型车（$ numCompactCars）已经创建。我是新来的深层（对我来说很深：p）OOP，所以如果我没有正确地做到这一点，请提供指导。非常感谢！

Answer 1

如果您将“新车”存储在一个数组中，您可以轻松地遍历它们并检查给定接口的实现。例如：

$cars['myCar'] = new HondaCivic(); 
$cars['myFriendCar'] = new ToyotaCorolla(); 

$compact_counter = 0; 
foreach ($cars as $car) 
    if ($car instanceof CompactCar) 
    $compact_counter ++; 

$compact_counter将有多少小型车已实施。

Answer 2

它看起来像我试图在界面上存储数据。这不是接口可以做的事情。接口用于描述类从外部看起来应该是什么样子，而不是实际实现的功能。

你想要什么可能是一个普通的类层次结构，如：

class Car { 

    public function doGeneralCarStuff() 
    { 
     //honk horn , blink blinkers, wipers on, yadda yadda 
    } 

} 

class CompactCar extends Car { 

    public static $numCompactCars = 0; 

    public function __construct() 
    { 
     self::$numCompactCars++; 
    } 

    public function doCompactCarStuff() 
    { 
     //foo and bar and foobar 
    } 
} 

class HondaCivic extends CompactCar { 

    public function __construct() 
    { 
     parent::__construct(); 
     // do Honda Civic stuff 
    } 

} 

class ToyotaCorolla extends CompactCar 
{ 
    public function __construct() 
    { 
     parent::__construct(); 
     // do Corolla stuff 
    } 
} 

$myCar = new HondaCivic(); 
$myFriendCar = new ToyotaCorolla(); 
echo CompactCar::$numCompactCars; // -> 2 

的界面会更适合用于描述不一定遗传特征，如：

interface HasSunroof { 
    function openSunroof(); 
    function closeSunroof(); 
} 

在一些语言（Javascript，Ruby等）HasSunroof可能是一个“mixin”并且具有与之相关的数据和功能，但是在PHP（以及Java等）中，必须将该功能放在实现该接口的类中。

接口（根据我的经验）在编译时类型检查的语言（比如Java）中比在“鸭子类型”语言（如PHP）中更常用。

Answer 3

工厂模式的唯一缺点是您可以随时绕过它 - 即new HondaCivic()会扰乱车辆数量。

这里的东西更强大的：

<?php 

interface Car 
{ 
    function doGeneralCarStuff(); 
} 

// Declare as abstract so it can't be instantiated directly 
abstract class CompactCar 
{ 
    // Increment car count 
    function __construct() { 
     CompactCar::$numCompactCars++; 
    } 
    function __clone() { 
     CompactCar::$numCompactCars++; 
    } 
    // Decrement car count 
    function __destruct() { 
     CompactCar::$numCompactCars--; 
    } 
    // Prevent external modification of car count 
    protected static $numCompactCars; 
    // Get the current car count 
    static public function getCount() { 
     return CompactCar::$numCompactCars; 
    } 
    // Require a compact car function for descendant classes 
    abstract public function doCompactCarStuff(); 
} 

// Extend and implement 
class HondaCivic extends CompactCar implements Car 
{ 
    function doGeneralCarStuff() { } 
    function doCompactCarStuff() { } 
} 

// Extend and implement 
class ToyotaCorolla extends CompactCar implements Car 
{ 
    function doGeneralCarStuff() { } 
    function doCompactCarStuff() { } 
} 

$myCar = new HondaCivic(); // 1 car 
$myFriendCar = new ToyotaCorolla(); // 2 cars 
printf("Number of compact cars: %d\n", CompactCar::getCount()); 
$myCar = new HondaCivic(); // still only 2 cars 
unset($myFriendCar); // one car left! 
printf("Number of compact cars: %d\n", CompactCar::getCount()); 
$myCar2 = clone $myCar; // now we have two cars again 
printf("Number of compact cars: %d\n", CompactCar::getCount()); 
CompactCar::$numCompactCars = 1000; // sorry, you can't do that!