ClickHouse/libs/libcommon/include/common/singleton.h

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#pragma once
/** Пример:
*
* class Derived : public Singleton<Derived>
* {
* friend class Singleton<Derived>;
* ...
* protected:
* Derived() {};
* };
*
* Или так:
*
* class Some
* {
* ...
* };
*
* class SomeSingleton : public Some, public Singleton<SomeSingleton> {}
*/
template<class Subject> class Singleton
{
public:
static Subject & instance()
{
/// Нормально при включенных thread safe statics в gcc (по-умолчанию).
static Subject instance;
return instance;
}
protected:
Singleton(){};
private:
Singleton(const Singleton&);
Singleton& operator=(const Singleton&);
};