抽象单例模式类 [英] Abstract Singleton pattern class

问题描述

我正在努力实现以下目标:

I'm trying to achieve the following goal:

使用此常规单例类:

abstract class Singleton {

    private static $instance = null;

    public static function self()
    {
      if(self::$instance == null)
      {   
         $c = __CLASS__;
         self::$instance = new $c;
      }

      return self::$instance;
    }
}

我很希望能够创建Singleton具体类，例如:

I'd love to be able to create Singleton concrete class such as:

class Registry extends Singleton {
    private function __construct() {}
    ...
}

，然后将它们用作:

Registry::self()->myAwesomePonyRelatedMethod();

但是显然地，__CLASS__旨在作为Singleton，因此发生致命错误，有关PHP无法实例化抽象类.但事实是，我希望实例化Registry(例如).

But obliviously __CLASS__ is intended as Singleton so a fatal error occurs about PHP not being able to instantiate an abstract class. But the truth is that I want Registry (for example) to be instantiated.

所以我尝试使用get_class($this)，但作为静态类，Singleton没有$ this.

So I tried with get_class($this) but being a static class, Singleton has no $this.

我该怎么做才能使其正常工作?

What could I do to make it work?

推荐答案

我的幻灯片中的删节代码 PHP中的子句-为什么它们不好，以及如何从应用程序中消除它们:

Abridged code from my Slides Singletons in PHP - Why they are bad and how you can eliminate them from your applications:

abstract class Singleton
{
    public static function getInstance()
    {
        return isset(static::$instance)
            ? static::$instance
            : static::$instance = new static();
    }

    final private function __construct()
    {
        static::init();
    }

    final public function __clone() {
        throw new Exception('Not Allowed');
    }

    final public function __wakeup() {
        throw new Exception('Not Allowed');
    }

    protected function init()
    {}
}

那你就可以做

class A extends Singleton
{
    protected static $instance;
}

如果需要执行其他设置逻辑，请覆盖扩展类中的init.

If you need to do additional setup logic override init in the extending class.

另请参见在PHP中具有用于数据库访问的单例的用例吗?

这篇关于抽象单例模式类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！