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Error while using qmlRegisterType

  • Hi all,
    Sorry if I'm creating a duplicated topic but I haven't found any solution that works for me.

    I'm newbie in Qt and currently I'm creating a C++ class named UserModel for using in qml file. This class calls a Restfull services then receives the result.

    Here's the Header:

    #ifndef USERMODEL_H
    #define USERMODEL_H
    #include <QObject>
    #include <QString>
    #include <QtNetwork>
    #include <QtNetwork/QNetworkRequest>
    #include <QtNetwork/QNetworkReply>
    class UserModel : public QObject
        explicit UserModel(QObject *parent = Q_NULLPTR);
        QByteArray response;
        QNetworkReply::NetworkError error_type;
        QString error_str;
        //This calls the restfull service
        Q_INVOKABLE int checkLogin(QString username, QString password);
        void executionFinished(UserModel *userModel);
    public slots:
        void replyFinished(QNetworkReply *reply);
    #endif // USERMODEL_H

    In main.cpp file, after including header I used following line:

    qmlRegisterType<UserModel>("com.quasimodo.user", 1, 0, "QUserModel");

    However I have got these errors:

    C:\Qt\Qt5.7.0\5.7\mingw53_32\include\QtQml\qqmlprivate.h:108: error: use of deleted function 'QQmlPrivate::QQmlElement<UserModel>::QQmlElement()'
    void createInto(void *memory) { new (memory) QQmlElement<T>; }

    C:\Qt\Qt5.7.0\5.7\mingw53_32\include\QtQml\qqmlprivate.h:99: error: call of overloaded 'UserModel()' is ambiguous

    Detailed built error:
    alt text

    Could anyone please show me what is the problem here?
    Any help is much appreciated!

  • Lifetime Qt Champion


    qqmlprivate.h:108: error: use of deleted function

    This sounds like you try to create a copy of QObject
    You are not allowed to clone or copy UserModel as its a QObject.
    Maybe you try to put in a list ? Then list should be declared as UserModel *

    Sorry picture is very small. Cannot read it.

  • Moderators

    Your constructors are wrong (and I assume this is the reason QQmlPrivate::createInto fails). Consider your declaration:

    explicit UserModel(QObject *parent = Q_NULLPTR);

    and now suppose I create an instance of that class, e.g.:

    UserModel myModel;

    How is the compiler supposed to know which of these two functions to call? They both match default construction. Fix this (by removing the implicit constructor for example) and see if the situation improves.

  • Thank you @mrjj very much for your support.

    I updated the picture. Sorry but could you please explain a little bit more?

    Here is my main.cpp file:

    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QQmlContext>
    #include <usermodel.h>
    int main(int argc, char *argv[])
        QGuiApplication app(argc, argv);
        qmlRegisterType<UserModel>("com.quasimodo.user", 1, 0, "QUserModel");
        QQmlApplicationEngine engine;
        return app.exec();

    Here is my qml file:

    import QtQuick 2.7
    import com.quasimodo.user 1.0
    Page1Form {
            id: user
        button_Login.onClicked: {
            if (user.checkLogin(textInput_UserName.text.toString(), textInput_Password.text.toString()) === 1)

    and that's all for my project.


  • Lifetime Qt Champion

    Well @kshegunov nailed it :)
    (same errors as when try to copy/clone object so though it was that. sorry)

  • Lifetime Qt Champion

    @Khang If you have these two constructors:

    explicit UserModel(QObject *parent = Q_NULLPTR);

    and then write

    UserModel myModel;

    then the compiler cannot decide which of the two constructors to call. How would you decide?
    Why do you have two constructors?
    This one should be enough: explicit UserModel(QObject *parent = Q_NULLPTR);

  • Thank you all for your help,
    Yes that's right. The problem is because there are 2 constructors. After I removed one then the program works fine.


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