Singleton

#include <iostream>

using namespace std;
class Singleton
{
public:
    static Singleton *getInstance()
    {
        if (_ins == nullptr)
            _ins = new Singleton;
        return _ins;
    }

private:
    static Singleton * _ins;
    Singleton(){}
    Singleton(const Singleton &){}
    Singleton operator=(const Singleton &){}
    ~Singleton(){}


};
Singleton *Singleton::_ins = nullptr;

int main(int argc, char *argv[])
{
    Singleton *p1 = Singleton::getInstance();
    Singleton *p2 = Singleton::getInstance();
    if (p1 == p2)
    {
        cout << "p1==p2" << endl;
    }
    return 0;
}

 A,B,C均要配置文件，xx.conf 不想使用全局变量 怎么办？->单例

//单例是共享数据，取代全局

config.h
#ifndef CONFIG_H
#define CONFIG_H
#include <iostream>
#include <string>
using namespace std;
struct info
{
    string ip;
    string port;
};

class Config
{
public:
    static Config *getInstance();
    string getIp();
    string getPort();
private:
    static Config *_ins;
    info _inf;
    Config();
    ~Config();
};

#endif // CONFIG_H

config.cpp
#include "config.h"
#include <fstream>
Config *Config::_ins = nullptr;
Config *Config::getInstance()
{
    if (_ins == nullptr)
        _ins = new Config;
    return _ins;
}

Config::Config()
{
    fstream fs;
    fs.open("/home/zzz/Workspace/pattern/Singleton/untitled/com.conf", ios::in|ios::out);
    if (!fs)
    {
        cout << "open error!";
    }
    fs >> _inf.ip;
    fs >>_inf.port;
    fs.close();
}


string Config::getIp()
{
    return _inf.ip;
}

string Config::getPort()
{
    return _inf.port;
}

a.h
#ifndef A_H
#define A_H

class A
{
public:
    A();
};

#endif

a.cpp
#include "a.h"
#include "config.h"
A::A()
{
    Config *conf = Config::getInstance();
    cout << "ip:" << conf->getIp() << endl;
    cout << "port:" << conf->getPort() << endl;
}

b.h
#ifndef B_H
#define B_H
class B
{
public:
    B();
};

#endif // B_H

b.cpp
#include "b.h"
#include "config.h"
B::B()
{
    Config *conf = Config::getInstance();
    cout << "ip:" << conf->getIp() << endl;
    cout << "port:" << conf->getPort() << endl;
}

c.h
#ifndef C_H
#define C_H
class C
{
public:
    C();
};

#endif // C_H

c.cpp
#include "c.h"
#include "config.h"
C::C()
{
    Config *conf = Config::getInstance();
    cout << "ip:" << conf->getIp() << endl;
    cout << "port:" << conf->getPort() << endl;
}