C++设计模式之单例模式

源代码在VC++ 6.0通过编译

//SingletonHeader.h
#include <IOSTREAM>
#include <FSTREAM>
#include <VECTOR>

class Logger{
public:
    static const std::string kLogLevelDebug;
    static const std::string kLogLevelInfo;
    static const std::string kLogLevelError;
    
    static Logger& instance();

    //Logs a single message at the given log level
    void log(const std::string& inMessage,
        const std::string& inLogLevel);
    //Logs a vector of message at the given log level
    void log(const std::vector<std::string>& inMessages,
        const std::string& inLogLevel);
    
    
protected:
    static Logger sInstance;
    static const char* const kLogFileName;
    std::ofstream mOutputStream;
    
private:
    Logger();
    virtual ~Logger();
};

//SingletonHeader.cpp
#include "SingletonHeader.h"
#include <STRING>
using namespace std;

const string Logger::kLogLevelDebug = "DEBUG";
const string Logger::kLogLevelInfo = "INFO";
const string Logger::kLogLevelError = "ERROR";

const char* const Logger::kLogFileName = "log.out";

Logger Logger::sInstance;

Logger& Logger::instance()
{
    return sInstance;
}

Logger::Logger()
{
    mOutputStream.open(kLogFileName,ios_base::app);
    if (!mOutputStream.good())
    {
        cerr<<"Unable to initialize the Logger!"<<endl;
    }
}

Logger::~Logger()
{
    mOutputStream.close();
}


void Logger::log(const string& inMessage, const string& inLogLevel)
{
    mOutputStream << inLogLevel << ":" << inMessage << endl;
}

void Logger::log(const vector<string>& inMessages, const string& inLogLevel)
{
    for (size_t i=0;i<inMessages.size();i++)
    {
        log(inMessages[i],inLogLevel);
    }
}

int main(int argc, char **argv)
{
    Logger::instance().log("test message",Logger::kLogLevelDebug);
    vector<string> items;

    items.push_back("item1");
    items.push_back("item2");

    Logger::instance().log(items,Logger::kLogLevelError);

    return 0;
}