第一种情况:子类没有定义构造函数时,默认继承。
第二种情况:子类定义了构造函数,则不会被继承。
对于4.x,如果父类恰好定义了子类的同名函数,则会被当做子类的构造函数,实例代码如下:
- class A
- {
- function A()
- {
- echo "I am the constructor of A.<br>n";
- }
- function B()
- {
- echo "I am a regular function named B in class A.<br>n";
- echo "I am not a constructor in A.<br>n";
- }
- }
- class B extends A
- {
- function C()
- {
- echo "I am a regular function.<br>n";
- }
- }
-
- $b = new B;
上面的代码在php5中则会调用A而不会调用B()
PHP面向对象:接口实例
我们设计一个在线销售系统,用户部分设计如下,将用户分为,NormalUser, VipUser, InnerUser三种,要求根据用户的不同折扣计算用户购买产品的价格,并要求为以后扩展和维护预留空间,用户部分先声明了一个接口User,用户都是User的实现。
user.php代码如下:
- <?
-
-
-
-
-
- interface User{
- public function getName();
- public function setName($_name);
- public function getDiscount();
- }
- abstract class AbstractUser implements User{
- private $name = "";
- protected $discount = 0;
- protected $grade = "";
-
- public function __construct($_name){
- $this->setName($_name);
- }
- public function getName(){
- return $this->name;
- }
- public function setName($_name){
- $this->name = $_name;
- }
- public function getDiscount(){
- return $this->discount;
- }
-
- public function getGrade(){
- return $this->grade;
- }
- }
- class NormalUser extends AbstractUser {
- protected $discount = 1.0;
- protected $grade = "NormalUser";
- }
- class VipUser extends AbstractUser {
- protected $discount = 0.8;
- protected $grade = "VipUser";
- }
- class InnerUser extends AbstractUser {
- protected $discount = 0.7;
- protected $grade = "InnerUser";
- }
- ?>
关于产品,我们进行了如下设计,声明一个接口Product,然后从Product继承下Book接口,在线销售的图书最后是实现了Book接口的BookOnline类。
Product.php代码如下:
- <?
-
- Interface Product{
- public function getProductName();
- public function getProductPrice();
- }
- interface Book extends Product {
- public function getAuthor();
- }
- class BookOnline implements Book{
- private $productName;
- private $productPrice;
- private $author;
-
- public function __construct($_bookName){
- $this->productName = $_bookName;
-
-
- }
-
- public function getProductName(){
- return $this->productName;
- }
-
- public function getProductPrice(){
-
-
- $this->productPrice = 100;
- return $this->productPrice;
- }
-
- public function getAuthor(){
-
- return $this->author;
- }
- }
- ?>
关于结算,我们使用了独立的结算类,使用静态方法做计算,产品结算,注意参数类型,代码如下:
- <?
- include_once("User.php");
- include_once("Product.php");
-
- class ProductSettle{
- public static function finalPrice(User $_user,Product $_product,$number = 1){
- $price = $_user->getDiscount() * $_product->getProductPrice() * $number;
- return $price;
- }
- }
- ?>
下面的例子是实现,大家可以自己分析下,实例代码如下:
- <?
- include_once("./class/User.php");
- include_once("./class/Product.php");
- include_once("./class/ProductSettle.php");
- $number = 10;
- $book = new BookOnline("设计模式");
-
- $user = new NormalUser("Tom");
- $price = ProductSettle::finalPrice($user,$book,$number);
- $str = "您好,尊敬的用户 " . $user->getName() . " <br>";
- $str .= "您的级别是 ". $user->getGrade() .", <br>";
- $str .= "您的折扣是 " . $user->getDiscount() . "<br>";
- $str .= "购买 $number 本 《 ". $book->getProductName() ;
- $str .= "》的价格是 $price <br><br>";
- echo $str;
-
- $user = new vipUser("Tom");
- $price = ProductSettle::finalPrice($user,$book,$number);
- $str = "您好,尊敬的用户 " . $user->getName() . " <br>";
- $str .= "您的级别是 ". $user->getGrade() .", <br>";
- $str .= "您的折扣是 " . $user->getDiscount() . "<br>";
- $str .= "购买 $number 本 《 ". $book->getProductName() ;
- $str .= "》的价格是 $price <br><br>";
- echo $str;
- $user = new InnerUser("Tom");
- $price = ProductSettle::finalPrice($user,$book,$number);
- $str = "您好,尊敬的用户 " . $user->getName() . " <br>";
- $str .= "您的级别是 ". $user->getGrade() .", <br>";
- $str .= "您的折扣是 " . $user->getDiscount() . "<br>";
- $str .= "购买 $number 本 《 ". $book->getProductName() ;
- $str .= "》的价格是 $price <br><br>";
- echo $str;
- ?>
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