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C++ (Qt)
public:
    static FlagObject *instance;

C++ (Qt)
class Example : public QObject
{
    Q_OBJECT
public:
    explicit Example(QObject *parent = 0);
    static Example* instanse();
    //...
 
private:
    static Example* _instanse;
    //...
};

C++ (Qt)
Example* Example::_instanse = 0;
 
Example::Example(QObject *parent) :
    QObject(parent)
{
    if (!_instanse)
        _instanse = this;
    //...
}
 
Example *Example::instanse()
{
    return _instanse;
}

C++ (Qt)
    new Example(this);

C++ (Qt)
    Example* ex = Example::instanse();

C++ (Qt)
//--------------------------------------------------------------------------
// File: a_singleton.h
//
// Desc: An one-instance class
//--------------------------------------------------------------------------
 
#ifndef A_SINGLETON_H
#define A_SINGLETON_H
 
#include <QtGlobal>
 
// disable the warning regarding 'this' pointers being used in
// base member initializer list. Singletons rely on this action
// #pragma warning(disable : 4355)
 
//--------------------------------------------------------------------------
// Name: uSingleton
// Desc: A singleton is a type of class of which only one instance may
//    exist. This is commonly used for management classes used to
//    control system-wide resources.
//--------------------------------------------------------------------------
 
template <class T>
class uSingleton
{
public:
 
    // the singleton must be constructed with a reference to the controlled object
    //----------------------------------------------------------------------
    uSingleton(T& rObject)
    {
        Q_ASSERT_X(!s_pInstance, "constructor", "Only one instance of this class is permitted.");
        s_pInstance = &rObject;
    }
 
    // the singleton accessor
    //----------------------------------------------------------------------
    ~uSingleton()
    {
        Q_ASSERT_X(s_pInstance, "destructor", "The singleton instance is invalid.");
        s_pInstance = 0;
    }
 
    // the singleton accessor
    //----------------------------------------------------------------------
    static T& instance()
    {
        if(!s_pInstance)
            s_pInstance = new T();
        Q_ASSERT_X(s_pInstance, "instancing", "The singleton has not yet been created.");
        return (*s_pInstance);
    }
 
    // delete singleton
    static void deleteSingleton()
    {
        if(s_pInstance)
        {
            delete s_pInstance;
            s_pInstance = 0;
        }
    }
 
private:
    // Data...
    //----------------------------------------------------------------------
    static T* s_pInstance;
 
    // Nonexistant Functions...
    //----------------------------------------------------------------------
    uSingleton(const uSingleton& Src);
    uSingleton& operator=(const uSingleton& Src);
 
};
template <class T> T* uSingleton<T>::s_pInstance = 0;
 
#endif // A_SINGLETON_H
 

MY_CLASS.testFunc();

C++ (Qt)
static T* s_pInstance;
 

C++ (Qt)
static QScopedPointer<T> s_pInstance;
...
template <class T>
QScopedPointer<T> uSingleton<T>::s_pInstance;