Qt信号多重定义

Question

I don't understand, I have a header:

#pragma once

#include <QObject>
#include <QString>
#include <QtQml>
#include <qqml.h>
#include <iostream>

class MainWindow : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString userName READ userName WRITE setUserName NOTIFY userNameChanged)

public:
    explicit MainWindow(QObject *parent = nullptr);

    QString userName();

    void setUserName(const QString &userName);

public slots:

signals:
    void userNameChanged();

private:
    QString m_userName;
};

And the cpp:

#include "MyWindow.h"

MainWindow::MainWindow(QObject *parent) : QObject(parent)
{

}

QString MainWindow::userName()  {
    return m_userName;
}

void MainWindow::setUserName(const QString &userName) {
    std::cout << "SET USERNAME" << std::endl;
    m_userName = userName;
}

void MainWindow::userNameChanged() {
    std::cout << "UPDATED" << std::endl;
}

When I compile, I have an error:

/path/to/file/build/moc_MyWindow.cpp:169: error: multiple definition of `MainWindow::userNameChanged()'; MyWindow.o:/path/to/file/build/../project/Views/MyWindow.cpp:17: first defined here

I don't understand what is the problem.

Thank you

Answer 1

Don't define yourself the signal function, because MOC do that for you.

Answer 2

userNameChanged is a signal not a slot . You can emit this signal anywhere you want, and there is no need to implement it. It seems that you want to emit this signal once a user name is set in the setUserName function. So do it as follows:

void MainWindow::setUserName(const QString &userName) {
    std::cout << "SET USERNAME" << std::endl;
    m_userName = userName;
    emit userNameChanged;

}

and remove the implementation of MainWindow::userNameChanged() .