SingleActive

最新推荐文章于 2025-01-10 17:09:28 发布

不如学也

最新推荐文章于 2025-01-10 17:09:28 发布

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分类专栏： c++

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本文介绍了一个通用的单例活动模板类的实现，该类允许在运行时仅激活一个实例，并提供了设置当前活动实例、检查当前实例是否为活动状态以及获取活动实例的方法。这个模板类使用了std::unique_ptr进行智能指针管理，确保了资源的安全释放。

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#pragma once
//https://github.com/jose-villegas/VCTRenderer

#include <iostream>
#include<memory>
#include<string>
using namespace std;

template<class T> class SingleActive
{
public:
	static void ResetActive();
	/// <summary>
	/// Sets this instance as active.
	/// </summary>
	virtual void SetAsActive();
	/// <summary>
	/// Return whether this instance is the one marked as active.
	/// </summary>
	/// <returns></returns>
	bool IsActive();
	/// <summary>
	/// Returns the active instance;
	/// </summary>
	/// <returns></returns>
	static std::unique_ptr<T> &Active();
protected:
	/// <summary>
	/// The current instance marked as active
	/// </summary>
	static std::unique_ptr<T> current;
	~SingleActive();
};

template<class T>
std::unique_ptr<T> SingleActive<T>::current = nullptr;

template<class T>
SingleActive<T>::~SingleActive()
{
	// release ownership but don't delete
	if (static_cast<T *>(this) == current.get())
	{
		current.release();
	}
}

template <class T>
void SingleActive<T>::ResetActive()
{
	current.release();
	current.reset(static_cast<T *>(nullptr));
}

template<class T>
void SingleActive<T>::SetAsActive()
{
	current.release();
	current.reset(static_cast<T *>(this));
}

template <class T>
bool SingleActive<T>::IsActive()
{
	return current.get() == static_cast<T *>(this);
}

template<class T>
std::unique_ptr<T> &SingleActive<T>::Active()
{
	return current;
}


/*

class student :public SingleActive<student> {
public:
	string name;
	string id;
	student(string n, string i) :name(n), id(i) {}
};

int main()
{
	unique_ptr<student> s1(new student("Alice", "123"));
	unique_ptr<student> s2(new student("Alice2", "123"));
	unique_ptr<student> s3(new student("Alice3", "123"));
	s1->SetAsActive();
	//s2->SetAsActive();

	static auto&ss = student::Active();
	cout << " " << ss->name << "  " << ss->id << endl;


	while (1);
}
*/