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PHP面向对象开发之类中接口的应用(interface、implements)

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Jun 13, 2016 am 09:51 AM

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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 {
const NAME = "常量对象属性";

function fun1();
function fun2(); //抽象方法。
}

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 {
const NAME = "名称";
function fun1();
function fun2();
}

interface demo2 {
function fun3();
function fun4();
}

interface demo3 {
const TEST = "Test";
function fun5();
}

class MyPc implements demo, demo2 {
function fun1() {
  echo "++++++++++
";
}
function fun2() {
  echo "----------
";
}
function fun3() {
  echo "1111111111
";
}
function fun4() {
  echo "2222222222
";
}
}

class MyPs extends MyPc implements demo3 {
function fun5() {
echo "继承类后引用接口";
}
}
$p = new MyPs;
$p->fun1();
$p->fun2();
$p->fun3();
$p->fun4();
$p->fun5();
?>

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
interface User{
    function getDiscount();
    function getUserType();
}
//VIP用户接口实现
class VipUser implements User{
    // VIP 用户折扣系数
    private $discount = 0.8;
    function getDiscount() {
        return $this->discount;
    }
    function getUserType() {
        return "VIP用户";
    }
}
class Goods{
    var $price = 100;
    var $vc;
    //定义 User 接口类型参数，这时并不知道是什么用户
    function run(User $vc){
        $this->vc = $vc;
        $discount = $this->vc->getDiscount();
$usertype = $this->vc->getUserType();
        echo $usertype."商品价格：".$this->price*$discount;
    }
}

$display = new Goods();
$display ->run(new VipUser); //可以是更多其他用户类型
?>

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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