c++ - C2248 : cannot access private member declared in Singleton class如何解决

Question

请帮忙... 我有单例类，但无法获取它的实例。

dbinfogetterdao.h

#ifndef MATRIXGETTERDAO_H
#define MATRIXGETTERDAO_H
#include <QtSql/QSqlDatabase>

namespace Ui{
    class DBInfoGetterDAO;
}

class DBInfoGetterDAO
{
    public:
        static DBInfoGetterDAO& getInstance();
    private:
        DBInfoGetterDAO();                   
        DBInfoGetterDAO(DBInfoGetterDAO const&);              
        void operator=(DBInfoGetterDAO const&); 
};

#endif // MATRIXGETTERDAO_H

dbinfogetterdao.cpp

#include "dbinfogetterdao.h"
#include <QtSql/QSqlDatabase>
#include <QDebug>
#include <QSqlError>
#include <QSqlQuery>


DBInfoGetterDAO& DBInfoGetterDAO::getInstance()
{
    static DBInfoGetterDAO instance;
    return instance;
}

DBInfoGetterDAO::DBInfoGetterDAO()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("mdpschema");
    db.setUserName("root");
    db.setPassword("password");
    bool ok = db.open();
    qDebug() << "db connection status = " << ok;
    QSqlError error = db.lastError();
    if (ok == false){
        qDebug() << "error text = " + error.text();
    }
}

我这样创建实例:

   DBInfoGetterDAO dbInfoGetterDAO = DBInfoGetterDAO::getInstance(); 

请你解释一下我做错了什么。

Answer 1

你的构造函数是私有(private)的，所以你不能创建你的类的对象。