php 语言特性学习（三）

摘要：当有值改变时调用实现类继承观察类的方法即完成通知方法里面可以写被通知之后的操作，如打印字符串等等观察者模式给程序员一个鼓励呗微信支付宝

1.__get __set

class  Test {
    private $arr = array(
        "x"=>null,
        "y"=>null
    );

    function __get($property) {
        if(array_key_exists($property,$this->arr)) {
            return $this->arr[$property];
        } else {
            print "error:can not read this property is not exist other than x or y
";
        }
    }

    function __set($property,$value) {
        if(array_key_exists($property,$this->arr)) {
            $this->arr[$property] = $value;
        } else {
            print "error:can not write this property is not exist other than x or y
";
        }
    }
}

$cl = new Test();
$cl->x = 1;
echo $cl->x;

$cl->t = 2;
echo $cl->t;

//结果是
1
error:can not write this property is not exist other than x or 
y 
error:can not read this property is not exist other than x or y

2.__call 函数使用

class HelloWorld {
    function display($time) {
        for($i=0;$i<$time;$i++) {
            print "hello world
";
        }
    }
}

class callHelloWorld {
    private $obj;
    function __construct() {
        $this->obj = new HelloWorld();
    }

    function __call($method,$arg) {
        return call_user_func_array(array($this->obj,$method),$arg);
    }
}

$me = new callHelloWorld();
$me->display(3);

结果是

hello world hello world hello world

3.迭代器

class numberSquare implements Iterator {
    private $start;
    private $end;
    private $cur;
    public function __construct($start, $end) {
        $this->start = $start;
        $this->end = $end;
    }

    public function rewind() {
        $this->cur = $this->start;
    }

    public function key() {
        return $this->cur;
    }

    public function current() {
        return pow($this->cur,3);
    }

    public function next() {
        $this->cur++;
    }

    public function valid() {
        return $this->cur <= $this->end;
    }
}

$obj = new numberSquare(2,5);
foreach($obj as $key => $value) {
    print "the square of $key is $value 

";
}

结果是

the square of 2 is 8 
the square of 3 is 27 
the square of 4 is 64 
the square of 5 is 125 

4.工厂模式

//定义抽象类 user类   读权限给，修改，删除权限不给
abstract class User {
    private $name = null;
    function __construct($name) {
        $this->name = $name ;
    }
    function getName() {
        return $this->name;
    }
    //权限方法
    function hasReadPermission() {
        return true;
    }
    function hasModifyPermission() {
        return false;
    }
    function hasDeletePermission() {
        return false;
    }
    //定制方法
    function wantsFlsahInterFace() {
        return true;
    }
}

class GuestUser extends User {
}

class CustomerUser extends User {
    //customer 有修改权限
    function hasModifyPermission() {
        return true ;
    }
}

class AdminUser extends User {
    function hasModifyPermission() {
        return true ;
    }
    function hasDeletePermission() {
        return true ;
    }
    function wantsFlsahInterFace() {
        return false;
    }
}

class UserFactory {
    private static $users = array(
        "andy"=>"Admin",
        "tom"=>"customer",
        "jack"=>"guest"
    );
    static function create($name) {
          switch(self::$users[$name]) {
            case "Admin" :
                return new AdminUser($name);
                  break;
            case "customer" :
                return new CustomerUser($name);
                break;
            case "guest" :
                return new GuestUser($name);
                break;
            default:
                break;
          }

    }
}

function boolToString($b) {
    if($b == true) {
        return "yes";
    } else {
        return "no";
    }
}

function displayPermission( $obj) {
        print $obj->getName() . ""s permission:
";
        print "Read: " . boolToString($obj->hasReadPermission());
        print "Modify: " . boolToString($obj->hasModifyPermission());
        print "Delete: " . boolToString($obj->hasDeletePermission());
}

function displayRequirement( $obj) {
    if($obj->wantsFlsahInterFace()) {
        print $obj->getName() . "require flash
";
    }
}

$login = array("andy","str","jack");
foreach($login as $key =>$val) {
    displayPermission(UserFactory::create($val));
}

结果是

received updated received updated
//实例化时不会有任何输出，直到有一个事件或者一个参数被设置才有所行动，一开始有一个观察类。实现类继承观察类，实现类里面有改变值的类在初始化的时候实例一下。当有值改变时调用实现类继承观察类的方法（即完成通知）方法里面可以写被通知之后的操作，如打印字符串等等

5.观察者模式

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