C++ 单例模式

有时候用到单例模式，记录一下。

另外，有时候也用 静态函数。

使用时，直接调用即可：

DatabaseManager::instance()->InsertSqlData("table", listField, listVal);

 

头文件：

有时候可能需要引用 include<QSharedPointer>

#ifndef DATABASEMANAGER_H
#define DATABASEMANAGER_H


#include "operatesqlite.h"
#include <QMutex>
#include <QMutexLocker>

class DatabaseManager
{
public:
    static QSharedPointer<DatabaseManager>& instance()
    {

        if (m_pInstance.isNull())
        {
            QMutexLocker mutexLocker(&m_Mutex);
            if (m_pInstance.isNull())
                m_pInstance = QSharedPointer<DatabaseManager>(new DatabaseManager());
        }
        return m_pInstance;
    }
private:
    DatabaseManager();
    DatabaseManager(const DatabaseManager&){}
    DatabaseManager& operator==(const DatabaseManager&){}
private:
    static QMutex m_Mutex;
    static QSharedPointer<DatabaseManager> m_pInstance;


public:
    //向表中插入数据
    bool InsertSqlData(QString tbName, QStringList& listField, QStringList& listVal);
    //记录是否存在
    bool IsRecordExist(const QString& tbName, const QString& field, const QString& value);
    bool GetRecordData(QString strSql);
    bool GetAirportInfo(QTableWidget* tbAirportInfo);
    bool DeleteRecord(const QString& tbName, const QString& field, const QString& fieldVal);

private:
    OperateSqlite   *m_pOperateSqlite;
};



#endif // DATABASEMANAGER_H

cpp文件：

#include "databasemanager.h"
#include <QSqlRecord>
#include <QDebug>

QMutex DatabaseManager::m_Mutex;
QSharedPointer<DatabaseManager> DatabaseManager::m_pInstance = nullptr;

DatabaseManager::DatabaseManager()
{
    m_pOperateSqlite = new OperateSqlite;
}

bool DatabaseManager::InsertSqlData(QString tbName, QStringList &listField, QStringList &listVal)
{
     return m_pOperateSqlite->InserSqlData(tbName, listField, listVal);
}

bool DatabaseManager::IsRecordExist(const QString &tbName, const QString &field, const QString &value)
{
    return m_pOperateSqlite->IsRecordExist1(tbName, field, value);
}

bool DatabaseManager::GetRecordData(QString strSql)
{
    QSqlQuery q(m_pOperateSqlite->GetSqlDataBase());
    //QString sql = "select * from tbAirportInfo";
    if(m_pOperateSqlite->GetRecordData(q, strSql)){
        int nNameIndex = q.record().indexOf("name");
        int nLongitudeIndex = q.record().indexOf("longitude");
        while (q.next()) {
            QString strName = q.value(nNameIndex).toString();
            QString strLongitude = q.value(nLongitudeIndex).toString();
            qDebug() << strName;
            qDebug() <<strLongitude;
        }
        return true;
    }
    return false;
}

bool DatabaseManager::GetAirportInfo(QTableWidget *tbAirportInfo)
{
    QSqlQuery q(m_pOperateSqlite->GetSqlDataBase());
    QString sql = "select * from tbAirportInfo";
    if(m_pOperateSqlite->GetRecordData(q, sql)){
        int nNameIndex = q.record().indexOf("name");
        int nLongitudeIndex = q.record().indexOf("longitude");
        int nLatitudeIndex = q.record().indexOf("latitude");
        while (q.next()) {
            QString strName = q.value(nNameIndex).toString();
            QString strLongitude = q.value(nLongitudeIndex).toString();
            QString strLatitude = q.value(nLatitudeIndex).toString();
            QStringList list;
            list << strName << strLongitude << strLatitude;

            int nRowCount = tbAirportInfo->rowCount();
            tbAirportInfo->setRowCount(nRowCount + 1);

            tbAirportInfo->setRowHeight(nRowCount, 60);
            QTableWidgetItem* item = new QTableWidgetItem(QString("%1").arg(nRowCount + 1));
            item->setTextAlignment(Qt::AlignCenter);
            tbAirportInfo->setItem(nRowCount, 0, item);
            for(int i = 0; i < list.size(); i++)
            {
                item = new QTableWidgetItem(list.at(i));
                item->setTextAlignment(Qt::AlignCenter);
                tbAirportInfo->setItem(nRowCount, i + 1, item);
            }
        }
        return true;
    }
    return false;
}

bool DatabaseManager::DeleteRecord(const QString &tbName, const QString &field, const QString& fieldVal)
{
    QSqlQuery q(m_pOperateSqlite->GetSqlDataBase());
    QString sql = QString("delete from %1 where %2 = '%3'").arg(tbName).arg(field).arg(fieldVal);
    return m_pOperateSqlite->ExecSql(sql);
}