I'm trying to get a QPushButton's action method running doing the following.

My login.h:

//
// Created by simon on 28.04.22.
//

#ifndef RESTCLIENT_LOGIN_H
#define RESTCLIENT_LOGIN_H

#include <QWidget>
#include <QPushButton>
#include <QLineEdit>


QT_BEGIN_NAMESPACE
namespace Ui { class Login; }
QT_END_NAMESPACE

class Login : public QWidget {
Q_OBJECT

QPushButton * loginButton;
QLineEdit * passwordInput;
QLineEdit * usernameInput;
QObject::connect(loginButton, &QPushButton::click, this, &buttonPressed);

public slots:
    void buttonPressed();

public:
    explicit Login(QWidget *parent = nullptr);

    ~Login() override;

private:
    Ui::Login *ui;
};


#endif //RESTCLIENT_LOGIN_H

The corresponding login.cpp:

#include "login.h"
#include "ui_Login.h"


Login::Login(QWidget *parent) :
        QWidget(parent), ui(new Ui::Login) {
    ui->setupUi(this);
}

Login::~Login() {
    delete ui;
}

void Login::buttonPressed() {
    //todo process login
}

The build fails, and Clion marks the code line containing the connect method in red. I'm aware that my attempt to connect the signal to my function is wrong, I hope someone can help me.

CodePudding user response：

The issue is that QPushButton::click() is not a signal, it is a function that performs a click.

The signal emitted when clicking the button is: QPushButton::clicked().

And as already mentioned, you should call the QObject::connect() function from inside a function (in the constructor for example). It makes no sense to call it in the class declaration.

CodePudding user response：

The connect call looks mostly fine, except that click is not a signal as Fareanor first noticed in his answer; use the clicked signal from QPushButton's base class QAbstractButton instead. See also QAbstractButton Signals for all available signals.

Additionally, connect needs to be inside of a function, not in the class declaration. The button needs to be initialized for the connection to work, so the constructor of your Login class seems like a logical place for it, for example:

Login::Login(QWidget *parent) :
        QWidget(parent), ui(new Ui::Login) {
    ui->setupUi(this);
    QObject::connect(loginButton, &QPushButton::clicked, this, &buttonPressed);
}

From the code you're showing it seems that loginButton is separate from the other GUI stuff in ui, so you probably also need to create that button first, i.e., adding , loginButton(new QPushButton) after ui(...), or move the loginButton to your .ui file...