c++日志单例实现

为了使项目的所有日志都打印到同一个日志中，必须使得所有类使用同一个日志，因此将日志类实现为单例。

.h文件

#pragma once#include<fstream>class LogHablee
{
private:LogHablee(std::string& dbg_dir);LogHablee(const LogHablee&) = delete;LogHablee& operator=(const LogHablee&) = delete;static LogHablee* _ins;	public:void getNowTimePrefix(std::string& now_time_prefix);public:static LogHablee* getInstance(std::string& dbg_dir){if (_ins == nullptr){_ins = new LogHablee(dbg_dir);}return _ins;}std::ofstream log;
};

.cpp文件

#include "LogHablee.h"
#include<string>LogHablee* LogHablee::_ins = nullptr;LogHablee::LogHablee(std::string& dbg_dir)
{std::string nowTimePrefix;getNowTimePrefix(nowTimePrefix);std::string logFilePath(dbg_dir + "/" + nowTimePrefix + "_log.txt");this->log.open(logFilePath, std::ios::trunc);
}void LogHablee::getNowTimePrefix(std::string& now_time_prefix)
{std::time_t now_time;struct tm* p = new tm;std::time(&now_time);localtime_s(p, &now_time);int year = p->tm_year + 1900;int month = p->tm_mon + 1;int day = p->tm_mday;int hour = p->tm_hour;int minute = p->tm_min;int second = p->tm_sec;delete p;// 20221130_134024: 2022年11月30日13点40分24秒now_time_prefix = std::to_string(year)+ std::string(2 - std::to_string(month).length(), '0') + std::to_string(month)+ std::string(2 - std::to_string(day).length(), '0') + std::to_string(day)+ "_"+ std::string(2 - std::to_string(hour).length(), '0') + std::to_string(hour)+ std::string(2 - std::to_string(minute).length(), '0') + std::to_string(minute)+ std::string(2 - std::to_string(second).length(), '0') + std::to_string(second);
}

另一个使用到log的类的.h文件

#pragma once
#include<string>class AClass
{
public:AClass(std::string& dbg_dir):_dbgDir(dbg_dir) {}void test();private:std::string _dbgDir;
};

# 另一个使用到log的类的.cpp文件

#include "AClass.h"
#include"LogHablee.h"void AClass::test()
{std::string nowTimePrefix;LogHablee* pHablee = LogHablee::getInstance(this->_dbgDir);pHablee->getNowTimePrefix(nowTimePrefix);pHablee->log << nowTimePrefix<< ": in AClass::test function"<< std::endl;
}

main函数

#include"LogHablee.h"
#include<iostream>
#include"AClass.h"int main()
{std::string nowTimePrefix;std::string dbgDir("./");LogHablee* pHablee = LogHablee::getInstance(dbgDir);pHablee->getNowTimePrefix(nowTimePrefix);pHablee->log << nowTimePrefix<< ": PROGRAM START, version 1.0.0.0"<< std::endl;AClass a(dbgDir);a.test(); // a.test()里面的日志内容也会写入到一开始创建的日志中return 0;
}