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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#pragma once
#include "utils_global.h"
#include <QMutex>
#include <QMutexLocker>
#include <type_traits>
#include <typeindex>
namespace Utils {
class Singleton;
struct SingletonStaticData
{
Singleton *m_instance = nullptr;
QMutex m_mutex;
};
class QTCREATOR_UTILS_EXPORT Singleton
{
Q_DISABLE_COPY_MOVE(Singleton)
public:
static void deleteAll();
private:
template <typename SingletonSubClass, typename ...Dependencies>
friend class SingletonWithOptionalDependencies;
Singleton() = default;
virtual ~Singleton();
static void addSingleton(Singleton *singleton);
static SingletonStaticData &staticData(std::type_index index);
};
template <typename SingletonSubClass, typename ...Dependencies>
class SingletonWithOptionalDependencies : public Singleton
{
public:
Q_DISABLE_COPY_MOVE(SingletonWithOptionalDependencies)
static SingletonSubClass *instance()
{
SingletonStaticData &data = staticData();
QMutexLocker locker(&data.m_mutex);
if (data.m_instance == nullptr) {
// instantiate all dependencies first
if constexpr (sizeof...(Dependencies))
instantiateDependencies<Dependencies...>();
data.m_instance = new SingletonSubClass;
// put instance into static list of registered instances
addSingleton(data.m_instance);
}
return static_cast<SingletonSubClass *>(data.m_instance);
}
protected:
SingletonWithOptionalDependencies() = default;
~SingletonWithOptionalDependencies() override
{
SingletonStaticData &data = staticData();
QMutexLocker locker(&data.m_mutex);
if (data.m_instance == this)
data.m_instance = nullptr;
}
private:
template <typename ...Dependency> static void instantiateDependencies()
{
static_assert ((... && std::is_base_of_v<Singleton, Dependency>),
"All Dependencies must derive from SingletonWithOptionalDependencies class.");
(..., Dependency::instance());
}
static SingletonStaticData &staticData()
{
static SingletonStaticData &data = Singleton::staticData(std::type_index(typeid(SingletonSubClass)));
return data;
}
};
} // namespace Utils
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