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POWhy doesn't this singleton pattern work?
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  1. POWhy doesn't this singleton pattern work?
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    copied!<p>I have two singletons, the first one's header looks like this (I've omitted everything that is not related to the Singleton pattern):</p> <pre><code>#ifndef TEXTUREMANAGER_DEFINED_H #define TEXTUREMANAGER_DEFINED_H class FontManager; class TextureManager { private: static TextureManager *instance; TextureManager(); public: FontManager *fontManager; static TextureManager* Instance(); }; #endif </code></pre> <p>And in the implementation, this is the Instance() method (and the initialization of the instance static member):</p> <pre><code>#include "FontManager.h" TextureManager * TextureManager::instance = 0; TextureManager* TextureManager::Instance () { if (instance==0) instance=new TextureManager; return instance; } </code></pre> <p>And this is the constructor:</p> <pre><code>TextureManager::TextureManager() { fontManager=FontManager::Instance(); } </code></pre> <p>The second singleton's (FontManager's) design is exactly the same, but instead of a FontManager pointer has a TextureManager pointer, and in it's constructor it initializes that pointer with TextureManager::Instance(). This should work like this: TextureManager is instanciated first (When the program starts), and in its constructor instanciates for the first time the FontManager singleton calling FontManager::Instance(). FontManager, in it's constructor, assigns its pointer to a TextureManager with TextureManager::Instance() and this method returns the TextureManager instance that already exists. Right?</p> <p>But instead of that the program enters an infinite loop because (I don't know why) the Instance() methods always create a new instance. I'ts like the <code>if (instance==0)</code> always evaluated to true.</p>
 

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