單例模式 基本版–單執行緒

#pragma once
#include <iostream>
#include <thread>
/**
 *單例模式標準實現 5步走（懶漢式）
 1靜態私有例項指標
 2拷貝賦值私有化
 3構造析構私有化
 4全域性訪問與釋放
 5靜態內部例項指標全域性例項
 *Date :[10/9/2018 ]
 *Author :[RS]
 */
using namespace std;
class Singleton1 {
private:
	Singleton1() {
		cout << "構造 begin" << endl;
		this_thread::sleep_for(chrono::seconds(1));
		cout << "構造 over" << endl;
	}
	virtual ~Singleton1() {
		cout << "構造" << endl;
	}
private:
	Singleton1(const Singleton1&) = delete;
	Singleton1& operator=(const Singleton1) = delete;
public:
	static Singleton1* GetInstance() {
		if (nullptr == mInstance) {
			mInstance = new Singleton1;
		}
		return mInstance;
	}
	static void RelaceInstance() {
		if (nullptr != mInstance) {
			delete mInstance;
			mInstance = nullptr;
		}
	}
public:
	void print() {
		cout << "列印例項記憶體指標：" << mInstance << endl;;
	}

private:
	static Singleton1 * mInstance;
};
Singleton1* Singleton1::mInstance = NULL;
 

測試方法

#include "Singleton1.hpp"

void main() {
	auto ss = Singleton1::GetInstance();
	ss->print();
	auto ss2 = Singleton1::GetInstance();
	ss2->print();
	system("pause");
}

測試結果