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QSqlQuery .lasterror compile error: invalid use of incomplete type 'class QSqlError'

  • Hi All,

    I'm trying to insert items into a mysql database. As I'm doing things wrong, I get returnvalue false from q.exec(); I would like to know what the error is, so I copied the construction from here:
    When compiling, I get the following error: invalid use of incomplete type 'class QSqlError'

    What is going on?

    09:06:06: Running steps for project untitled8...
    09:06:06: Starting: "C:\Qt\5.10.1\mingw53_32\bin\qmake.exe" C:\Users\crldewijs\Desktop\git\untitled8\ -spec win32-g++ "CONFIG+=debug" "CONFIG+=qml_debug"
    Info: creating stash file C:\Users\crldewijs\Desktop\git\build-untitled8-Desktop_Qt_5_10_1_MinGW_32bit-Debug\.qmake.stash
    09:06:07: The process "C:\Qt\5.10.1\mingw53_32\bin\qmake.exe" exited normally.
    09:06:07: Starting: "C:\Qt\Tools\mingw530_32\bin\mingw32-make.exe" qmake_all
    mingw32-make: Nothing to be done for 'qmake_all'.
    09:06:08: The process "C:\Qt\Tools\mingw530_32\bin\mingw32-make.exe" exited normally.
    09:06:08: Starting: "C:\Qt\Tools\mingw530_32\bin\mingw32-make.exe" 
    C:/Qt/Tools/mingw530_32/bin/mingw32-make -f Makefile.Debug
    mingw32-make[1]: Entering directory 'C:/Users/crldewijs/Desktop/git/build-untitled8-Desktop_Qt_5_10_1_MinGW_32bit-Debug'
    C:\Qt\5.10.1\mingw53_32\bin\uic.exe ..\untitled8\mainwindow.ui -o ui_mainwindow.h
    g++ -c -fno-keep-inline-dllexport -g -std=gnu++11 -Wall -W -Wextra -fexceptions -mthreads -DUNICODE -D_UNICODE -DWIN32 -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_SQL_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I..\untitled8 -I. -IC:\Qt\5.10.1\mingw53_32\include -IC:\Qt\5.10.1\mingw53_32\include\QtWidgets -IC:\Qt\5.10.1\mingw53_32\include\QtGui -IC:\Qt\5.10.1\mingw53_32\include\QtANGLE -IC:\Qt\5.10.1\mingw53_32\include\QtSql -IC:\Qt\5.10.1\mingw53_32\include\QtCore -Idebug -I. -IC:\Qt\5.10.1\mingw53_32\mkspecs\win32-g++  -o debug\main.o ..\untitled8\main.cpp
    g++ -c -fno-keep-inline-dllexport -g -std=gnu++11 -Wall -W -Wextra -fexceptions -mthreads -DUNICODE -D_UNICODE -DWIN32 -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_SQL_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I..\untitled8 -I. -IC:\Qt\5.10.1\mingw53_32\include -IC:\Qt\5.10.1\mingw53_32\include\QtWidgets -IC:\Qt\5.10.1\mingw53_32\include\QtGui -IC:\Qt\5.10.1\mingw53_32\include\QtANGLE -IC:\Qt\5.10.1\mingw53_32\include\QtSql -IC:\Qt\5.10.1\mingw53_32\include\QtCore -Idebug -I. -IC:\Qt\5.10.1\mingw53_32\mkspecs\win32-g++  -o debug\mainwindow.o ..\untitled8\mainwindow.cpp
    ..\untitled8\mainwindow.cpp: In constructor 'MainWindow::MainWindow(QWidget*)':
    ..\untitled8\mainwindow.cpp:17:29: error: invalid use of incomplete type 'class QSqlError'
         qDebug() << q.lastError(); // as per
    In file included from C:\Qt\5.10.1\mingw53_32\include\QtSql/QSqlDatabase:1:0,
                     from ..\untitled8\mainwindow.cpp:7:
    C:\Qt\5.10.1\mingw53_32\include\QtSql/qsqldatabase.h:49:7: note: forward declaration of 'class QSqlError'
     class QSqlError;
    Makefile.Debug:822: recipe for target 'debug/mainwindow.o' failed
    mingw32-make[1]: Leaving directory 'C:/Users/crldewijs/Desktop/git/build-untitled8-Desktop_Qt_5_10_1_MinGW_32bit-Debug'
    mingw32-make[1]: *** [debug/mainwindow.o] Error 1
    Makefile:36: recipe for target 'debug' failed
    mingw32-make: *** [debug] Error 2
    09:06:13: The process "C:\Qt\Tools\mingw530_32\bin\mingw32-make.exe" exited with code 2.
    Error while building/deploying project untitled8 (kit: Desktop Qt 5.10.1 MinGW 32bit)
    When executing step "Make"
    09:06:13: Elapsed time: 00:08.

    My program:

    # Project created by QtCreator 2018-07-23T08:59:04
    QT       += core gui sql
    greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
    TARGET = untitled8
    TEMPLATE = app
    # The following define makes your compiler emit warnings if you use
    # any feature of Qt which has been marked as deprecated (the exact warnings
    # depend on your compiler). Please consult the documentation of the
    # deprecated API in order to know how to port your code away from it.
    # You can also make your code fail to compile if you use deprecated APIs.
    # In order to do so, uncomment the following line.
    # You can also select to disable deprecated APIs only up to a certain version of Qt.
    #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
    SOURCES += \
            main.cpp \
    HEADERS += \
    FORMS += \
    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include <QDebug>
    #include <QtWidgets>
    #include <QWidget>
    #include <QSqlDatabase>
    #include <QSqlQuery>
    MainWindow::MainWindow(QWidget *parent) :
        ui(new Ui::MainWindow)
        QSqlQuery q;
        qDebug() << q.lastError(); // as per
        delete ui;

    My versions:
    Qt 5.10.1 mingw53_32
    Windows 7 Enterprise SP1

  • Moderators

    try adding #include <QSqlError>

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