如何调用作为插槽的qt函数

我正在使用由QT4生成GUI的开源代码。我想做的是稍微更改代码，此时需要在GUI上按下一个按钮。我想要的是要调用的函数，这样我就不必按下按钮来执行它

该函数是在公共插槽下的类tum_ardrone_gui中定义的。这个函数被称为SendClicked（），所以我通过定义一个对象来调用这个函数，比如：

tum_ardrone_gui* gui;
gui->SendClicked();

我遇到了一个错误，是我的语法错误，还是不允许我这样调用"slots"定义的函数？

提前感谢！

第1版：谢谢大家的帮助。这是我的主.cpp文件：

#include "../UINode/tum_ardrone_gui.h"
#include "../UINode/RosThread.h"
#include "../UINode/PingThread.h"
#include <QtGui>
#include <QApplication>
#include "ros/ros.h"
// this global var is used in getMS(ros::Time t) to convert to a consistent integer timestamp used internally pretty much everywhere.
// kind of an artifact from Windows-Version, where only that was available / used.
unsigned int ros_header_timestamp_base = 0;
int main(int argc, char *argv[])
{
std::cout << "Starting drone_gui Node" << std::endl;
// ROS
ros::init(argc, argv, "drone_guiuno");
RosThread t;
PingThread p;
// UI
QApplication a(argc, argv);
tum_ardrone_gui w;
// make them communicate with each other
t.gui = &w;
w.rosThread = &t;
p.gui = &w;
p.rosThread = &t;
w.pingThread = &p;
// start them.
t.startSystem();
p.startSystem();
w.show();

// Error 1):
//tum_ardrone_gui gui = new tum_ardrone_gui(); 
//gui->SendClicked();
//delete gui;
// DOES NOT COMPILE: ERROR MESSAGE /usr/include/qt4/QtGui/qwidget.h: In copy constructor ‘tum_ardrone_gui::tum_ardrone_gui(const tum_ardrone_gui&)’:
// /usr/include/qt4/QtGui/qwidget.h:806:5: error: ‘QWidget::QWidget(const QWidget&)’ is private
//Error 2): Compiles and works! But why didn't the above?
w.SendClicked();

// wait until windows closed....
int ec = a.exec();
 // stop ROS again....
t.stopSystem();
p.stopSystem();
std::cout << "Exiting drone_gui Node" << std::endl;
return ec;
}