PHP面向对象开发之类中接口的应用(interface、implements)
php类中接口的应用关键字是interface、implements了,接口是一种成员属性全部为抽象或常量的特殊抽象类,下面我们看几个实例。
类中接口的应用
1.关键字:interface
2.关键字:implements
1.接口的介绍与创建
接口:一种成员属性全部为抽象或常量的特殊抽象类。
规则:
1.类中全部为抽象方法。
2.抽象方法钱不用加abstract。
3.接口抽象方法属性为public。
4.成员属性必须为常量。
格式:
代码如下 | 复制代码 |
interface demo { function fun1(); |
2.接口的应用与规范
接口引用区别于类继承关键字 extends ,继承只能只是单一性,而接口可以使用关键字 implements 多个引用并用逗号分开
1.格式:普通类引用接口
class MyPc implements demo , demo2 , demo3 {
...
}
2.格式:抽象类应用接口例子
abstract class MyPc implements demo , demo2 , demo3 {
...
}
3.格式:继承父类引用接口并存
class MyPc extends Root implements demo , demo2 , demo3 {
...
}
先继承后接口,单继承多接口。
4.格式:接口与接口的继承
interface demo3 extends demo {
...
}
实例:
代码如下 | 复制代码 |
interface demo { interface demo2 { interface demo3 { class MyPc implements demo, demo2 { class MyPs extends MyPc implements demo3 { |
例
接口使用关键字 interface 来定义,并使用关键字 implements 来实现接口中的方法,且必须完全实现。
例子:
代码如下 | 复制代码 |
//定义接口 $display = new Goods(); |
运行该例子,输出:
VIP用户商品价格:80 元
该例子演示了一个 PHP 接口的简单应用。该例子中,User 接口实现用户的折扣,而在 VipUser 类里面实现了具体的折扣系数。最后商品类 Goods 根据 User 接口来实现不同的用户报价。
该例子仅限于演示 PHP 接口的用法,不涉及其科学与否。
实现多个接口
PHP也可以在继承一个类的时候同时实现多个接口:
class 子类 extends 父类 implemtns 接口1, 接口2, ...
{
......
}
抽象类和接口的区别
接口是特殊的抽象类,也可以看做是一个模型的规范。接口与抽象类大致区别如下:
1.一个子类如果 implements 一个接口,就必须实现接口中的所有方法(不管是否需要);如果是继承一个抽象类,只需要实现需要的方法即可。
2.如果一个接口中定义的方法名改变了,那么所有实现此接口的子类需要同步更新方法名;而抽象类中如果方法名改变了,其子类对应的方法名将不受影响,只是变成了一个新的方法而已(相对老的方法实现)。
3.抽象类只能单继承,当一个子类需要实现的功能需要继承自多个父类时,就必须使用接口。

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