QT signal slot summary -connect function incorrect usage

QT Library qobject.h
connect Function declaration ：connect The function is used to establish the connection between the signal and the slot ,QT The library provides three implementations ：

    static QMetaObject::Connection connect(const QObject *sender, const char *signal,
                        const QObject *receiver, const char *member, Qt::ConnectionType = Qt::AutoConnection);

static QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal,
                    const QObject *receiver, const QMetaMethod &method,
                    Qt::ConnectionType type = Qt::AutoConnection);

    inline QMetaObject::Connection connect(const QObject *sender, const char *signal,
                        const char *member, Qt::ConnectionType type = Qt::AutoConnection) const;

class ConnectCamera : public QWidget
{
	Q_OBJECT

public:
	ConnectCamera(QWidget *parent = Q_NULLPTR);
	~ConnectCamera();
	
public slots:
	void onConnectBtnSolt();
	void onCancelBtSolt();
	void onErrorMess(const QString & _errorMess);
signals:
	void signalConnectCamera(const QString& _ip, const QString& _user, const QString& _pass);
private:
	Ui::ConnectCamera ui;
};

Use QT The first implementation provided by the Library , To bind signals to slots
Proper use 1：

connect(ui.okButton, SIGNAL(clicked()), this, SLOT(onConnectBtnSolt()));
connect(ui.cancelButton, SIGNAL(clicked()), this, SLOT(onCancelBtSolt()));

Incorrect usage 1：

connect(ui.okButton, SIGNAL(clicked()), this, SLOT(onConnectBtnSolt));

Cause analysis ：
usage 1 Called connect Function is actually ：

static QMetaObject::Connection connect(const QObject *sender, const char *signal,
                        const QObject *receiver, const char *member, Qt::ConnectionType = Qt::AutoConnection);
                        
// SLOT The definition of 
Q_CORE_EXPORT const char *qFlagLocation(const char *method);
# define SLOT(a)     qFlagLocation("1"#a QLOCATION)

qt The signal slot in , The callback function is actually used ,onConnectBtnSolt（） Is parsed as a function ,onConnectBtnSolt Format judgment will make mistakes
A very detailed explanation on the Internet ,QT The version may be earlier than 5.9.6
QT QObject：：connect Function learning