Question

尝试使用扩展单线的对象，但我无法做到。如何从扩展类调用方法？

如何用单身人士显示13个非12人？

class SingletonTest
{
    protected static $_instance;

    private function __construct(){}

    private function __clone(){}

    public static function getInstance() {

        if (null === self::$_instance) {
            self::$_instance = new self();
        }

        return self::$_instance;
    }

    public function test2(){
        return 12;
    }
}


class ExtendSingleton extends SingletonTest
{
    public function test2() {
        return 13;
    }
}


$b = ExtendSingleton::getInstance();
echo $b->test2(); //12

Answer 1

public static function getInstance()
{
    static $instances = array();

    $calledClass = get_called_class();

    if (!isset($instances[$calledClass]))
    {
        $instances[$calledClass] = new $calledClass();
    }

    return $instances[$calledClass];
}

Answer 2

如果使用静态绑定关键字“static”而不是“self”

，您将获得所需的内容

class SingletonTest
{
    protected static $_instance;

    private function __construct(){}

    private function __clone(){}

    public static function getInstance() {

        if (null === static::$_instance) {
            static::$_instance = new static();
        }

        return static::$_instance;
    }

    public function test2(){
        return 12;
    }
}


class ExtendSingleton extends SingletonTest
{
    public function test2() {
        return 13;
    }
}


$b = ExtendSingleton::getInstance();
echo $b->test2(); //13

$a = SingletonTest::getInstance();
echo $a->test2(); //13

exit;

但正如您在上面的示例中看到的那样，您将首先调用“getInstance”的类将在$ _instance字段中存储它的实例。

无法创建基本单线类并继承单线态行为。

Answer 3

所以这对你有用：

（首先通常函数是公共的，所以如果你从另一个类延伸，你可以使用它们！你需要从ExtendSingleton而不是SingletonTest来自ExtendSingleton exdend的对象 - ＆gt; SingletonTest而不是其他方式。）

<?php

    class SingletonTest {

        protected static $_instance;

        public function __construct() {

        }

        public function __clone() {

        }

        public static function getInstance() {

            if (null === self::$_instance) {
                self::$_instance = new self();
            }

            return self::$_instance;
        }

        public function test2(){
            return 12;
        }
    }


    class ExtendSingleton extends SingletonTest {

        public function test2() {
            return 13;
        }

    }


    $b = new ExtendSingleton();
    echo $b->test2(); //13


?>

输出：

Answer 4

我已经测试了bicccio的解决方案并且可以正常使用

class SingletonTest
{
    protected static $_instances = [];

    private function __construct(){}

    private function __clone(){}

    public static function getInstance()
    {
        $calledClass = get_called_class();

        if (!isset(self::$_instances[$calledClass]))
        {
            self::$_instances[$calledClass] = new $calledClass();
        }

        return self::$_instances[$calledClass];
    }

    public function test2(){
        return 12;
    }
}


class ExtendSingleton extends SingletonTest
{
    public function test2() {
        return 13;
    }
}


$b = ExtendSingleton::getInstance();
echo $b->test2(); //13

$a = SingletonTest::getInstance();
echo $a->test2(); //12

Answer 5

你可以使用后期静态绑定在php中扩展单例类，整个过程在这个问题中得到了很好的讨论。

Creating the Singleton design pattern in PHP5

PHP如何从扩展类调用方法

5 个答案: