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  1. 24th August 2016, 17:41 #6
    jfinn88
    jfinn88 is offline Intermediate user
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    Default Re: using an isntance of QSqlDatabase for connection defiinition

    I have two classes I need to use an instance variable of the class QSqlDatabase to set database connections. I created an instance variable of the QSqlDatabase class in both classes under private:
    --------------- Header file----------------
    Qt Code: 
    1. //Data struct for user event log
    2. struct userEventLogMsg{
    3.     //hold all values for a single list entry,
    4.   QString id;
    5.   QString username;
    6.   QString eventmessage;
    7.   QString datetime;
    8. };
    9.  
    10. //---Class UserEventDailyLog responsible for XMUI UserEvnetLog | Subed classed: QAbstractTableModel---//
    11. class UserEventLog : public QAbstractListModel
    12. {
    13.     Q_OBJECT
    14.  
    15. public:
    16.     explicit UserEventLog(QObject *parent = 0);
    17.  
    18.     ~UserEventLog();
    19.  
    20.     enum userEventRoles {idRole= Qt::UserRole + 220, nameRole, msgRole, dateRole};
    21.  
    22.     int rowCount(const QModelIndex & parent) const;
    23.  
    24.     QHash<int, QByteArray> roleNames() const;
    25.  
    26.     QVariant data(const QModelIndex &index, int role=Qt::DisplayRole) const;
    27.  
    28.     Q_INVOKABLE void addEvent(const userEventLogMsg &msg);
    29.  
    30.     void dbConnect();
    31.  
    32.     void sqlSelect();
    33.  
    34. private:
    35.     QList<userEventLogMsg> m_userEventList;
    36.     QSqlDatabase m_selectDataBase;
    37. };
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    Qt Code: 
    1. //---------CPP file--------------//
    2. //
    3. //  UserEventLogModel
    4. //
    5.  
    6. //---Constructor---//
    7. UserEventLog::UserEventLog(QObject *parent):QAbstractListModel(parent) {
    8.  
    9. }
    10. //---Destructor---//
    11. UserEventLog::~UserEventLog() {
    12.  
    13. }
    14.  
    15. int UserEventLog::rowCount(const QModelIndex &parent) const {
    16.     Q_UNUSED(parent);
    17.     qDebug()<< m_userEventList.count();
    18.     return m_userEventList.count();
    19. }
    20.  
    21. QHash<int, QByteArray> UserEventLog::roleNames() const {
    22.     QHash<int, QByteArray> roleNames;
    23.     roleNames.insert(idRole, "id");
    24.     roleNames.insert(nameRole, "userName");
    25.     roleNames.insert(msgRole, "eventMessage");
    26.     roleNames.insert(dateRole, "dateTime");
    27.     qDebug()<< roleNames;
    28.     return roleNames;
    29. }
    30.  
    31. QVariant UserEventLog::data(const QModelIndex &index, int role) const {
    32.     if (index.row() < 0 || index.row() >= m_userEventList.count()){
    33.         return QVariant();
    34.     }
    35.  
    36.     QVariant text;
    37.  
    38.     if(role == idRole) {
    39.         userEventLogMsg msg = m_userEventList.at(index.row());
    40.         text = msg.id;
    41.         qDebug() << text;
    42.     }
    43.     else if(role == nameRole) {
    44.         userEventLogMsg msg = m_userEventList.at(index.row());
    45.         text = msg.username;
    46.         qDebug() << text;
    47.     }
    48.     else if(role == msgRole) {
    49.         userEventLogMsg msg = m_userEventList.at(index.row());
    50.         text = msg.eventmessage;
    51.         qDebug() << text;
    52.     }
    53.     if(role == dateRole) {
    54.         userEventLogMsg msg = m_userEventList.at(index.row());
    55.         text = msg.datetime;
    56.         qDebug() << text;
    57.     }
    58.     return text;
    59. }
    60.  
    61. void UserEventLog::addEvent(const userEventLogMsg &msg) {
    62.  
    63.     beginInsertRows(QModelIndex(), 0, 0);
    64.     m_userEventList.insert(0, msg);
    65.     endInsertRows();
    66. }
    67.  
    68. void UserEventLog::dbConnect() {
    69.     m_selectDataBase = QSqlDatabase::addDatabase("QSQLITE", "conn2");
    70.     qDebug() << m_selectDataBase.isValid();
    71.     m_selectDataBase.setDatabaseName("/home/amet/userLog.db");
    72.     m_selectDataBase.open();
    73.  
    74.     if(!m_selectDataBase.open()){
    75.        qDebug() <<"error in opening DB";
    76.     }
    77.     else{
    78.        qDebug() <<"connected to DB" ;
    79.     }
    80. }
    81. void UserEventLog::sqlSelect() {
    82.  
    83.     //m_selectDataBase = QSqlDatabase::database("conn2");
    84.     qDebug() << m_selectDataBase.isValid();
    85.     m_selectDataBase.open();
    86.     QSqlQuery selectQuery;
    87.     selectQuery.prepare("SELECT id, userName, eventMessage, dateTime FROM userlogevents");
    88.     qDebug() <<selectQuery.lastError();
    89.  
    90.     if(selectQuery.exec()){
    91.         qDebug()<<"sql statement exicuted fine";
    92.     }
    93.     else{
    94.         qDebug() <<"Errors accured with sql statement";
    95.         qDebug() <<selectQuery.lastError();
    96.     }
    97.  
    98.     while (selectQuery.next()){
    99.         userEventLogMsg msg;
    100.         UserEventLog model;
    101.         msg.id = selectQuery.value(0).toString();
    102.         msg.username = selectQuery.value(1).toString();
    103.         msg.eventmessage = selectQuery.value(2).toString();
    104.         msg.datetime = selectQuery.value(3).toString();
    105.         model.addEvent(msg);
    106.     }
    107.     //m_selectDataBase.close();
    108.     //m_selectDataBase.removeDatabase("conn2");
    109. }
    110. //----------------------------------------------------------------//
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    my other class that need a database connection to the same database

    ---------CPP file-----------
    Qt Code: 
    1. void XMUI::hdpiWindow()
    2. {
    3.     mUserEventLogModel = new UserEventLog();
    4.     mUserEventLogModel->dbConnect();
    5.     mUserEventLogModel->sqlSelect();
    6.     m_QmlEngine->rootContext()->setContextProperty("UserEventLog", mUserEventLogModel);
    7. }
    8.  
    9. void XMUI::insertLogMessage(QString msg)
    10. {
    11.     m_insertDataBase = QSqlDatabase::addDatabase("QSQLITE", "conn1");
    12.     m_insertDataBase.setDatabaseName("/home/amet/userLog.db");
    13.     m_insertDataBase.open();
    14.  
    15.     if(m_insertDataBase.isOpen()){
    16.  
    17.        qDebug() <<"connected to DB" ;
    18.     }
    19.     else{
    20.         qDebug() <<"error in opening DB";
    21.         m_insertDataBase.open();
    22.     }
    23.  
    24.     qDebug() << "insert Log Message called";
    25.     QSqlQuery insertQuery(m_insertDataBase);
    26.     insertQuery.prepare("INSERT INTO userlogevents (firstName, lastName, userName, eventMessage, dateTime) VALUES('John', 'Doe', 'JohnnyD', ':eventMessage', datetime(current_timestamp))");
    27.     insertQuery.bindValue(":eventMessage", msg);
    28.     insertQuery.exec();
    29.     //m_insertDataBase.close();
    30.     //m_insertDataBase.removeDatabase("conn1");
    31. }
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    ----header file--------
    Qt Code: 
    1. class XMUI : public QObject
    2. {
    3.     Q_OBJECT
    4.  
    5. public:
    6.     explicit XMUI(QQuickWidget* _quickWidget);
    7.  
    8.     void hdpiWindow();
    9.  
    10.     Q_INVOKABLE void insertLogMessage(QString msg);
    11.  
    12. private:
    13.     QSqlDatabase m_insertDataBase;
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    Added after 18 minutes:


    Quote Originally Posted by anda_skoa View Post
    Yes


    You pass the QSqlDatabase handle to the QSqlQuery constructor.
    Qt Code: 
    1. QSqlQuery insertQuery(m_insertDataBase);
    2. insertQuery.prepare(...);
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    I was passing the name of my connection not the instance variable, changed it to instance variable.

    Qt Code: 
    1. if (!m_insertDataBase.isValid() {
    2.     // addDatabase, setDatabaseName
    3. }
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    Cheers,
    _
    I moved the add and set methods inside an if condition to set them if the database is not valid. However I get confused because I need to connect to the database to begin with... If I'm only setting them when it not valid how do I initially set the connect the first time. set it in the constructor?

    Qt Code: 
    1. void XMUI::insertLogMessage(QString msg)
    2. {
    3.      //qDebug() << m_insertDataBase.connectionNames();
    4.  
    5.     if(!m_insertDataBase.isValid()){
    6.        qDebug() <<"error in opening DB";
    7.        m_insertDataBase = QSqlDatabase::addDatabase("QSQLITE", "conn1");
    8.        m_insertDataBase.setDatabaseName("/home/amet/userLog.db");
    9.        qDebug() << m_insertDataBase.connectionNames();
    10.     }
    11.     else{
    12.         qDebug() <<"connected to DB";
    13.         m_insertDataBase.open();
    14.         //qDebug() << m_insertDataBase.lastError();
    15.     }
    16.  
    17.     m_insertDataBase.open();
    18.     QSqlQuery m_insertQuery(m_insertDataBase);
    19.     m_insertQuery.prepare("INSERT INTO userlogevents (firstName, lastName, userName, eventMessage, dateTime) VALUES('John', 'Doe', 'JohnnyD', ':eventMessage', datetime(current_timestamp))");
    20.     m_insertQuery.bindValue(":eventMessage", msg);
    21.     m_insertQuery.exec();
    22.     qDebug() << m_insertQuery.lastError();
    23.     //m_insertDataBase.close();
    24.     //QSqlDatabase::removeDatabase("conn1");
    25. }
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    Last edited by jfinn88; 24th August 2016 at 21:38.
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