How to exit a "game" in Qt when health is 0 - qt

Question

I'm quite new to Qt, but I got into it to start experimenting with making 2D games. I've got a extremely rough and simple game started, but I have an issue. Whenever the health gets to 0, the game doesn't end. I just want to know how to end the game and where to put this exit command before making a "Game Over" screen. My code is below, and from what I can grasp, I assume the QApplication::quit() goes in the Game.cpp file. Doing this by taking the health integer from Health.cpp and Health.h and putting it in Game.cpp. Any help is appreciated. Here is the code I feel the answers lie in, if more info is needed, ask.
Game.h
#ifndef GAME_H
#define GAME_H
#include <QGraphicsView>
#include <QWidget>
#include <QGraphicsScene>
#include "Player.h"
#include "Score.h"
#include "Health.h"
#include "Level.h"
#include "Main.h"
class Game: public QGraphicsView{
public:
Game(QWidget * parent=0);
QGraphicsScene * scene;
Player * player;
Score * score;
Health * health;
Level * level;
Main * close;
int end();
};
#endif // GAME_H
Game.cpp
#include "Game.h"
#include <QTimer>
#include <QGraphicsTextItem>
#include <QFont>
#include "Enemy.h"
#include <QMediaPlayer>
#include <QBrush>
#include <QImage>
#include <QApplication>
Game::Game(QWidget *parent){
// create the scene
scene = new QGraphicsScene();
scene->setSceneRect(0,0,800,600); // make the scene 800x600 instead of infinity by infinity (default)
setBackgroundBrush(QBrush(QImage(":/images/bg.png")));
// make the newly created scene the scene to visualize (since Game is a QGraphicsView Widget,
// it can be used to visualize scenes)
setScene(scene);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setFixedSize(800,600);
// create the player
player = new Player();
player->setPos(400,500); // TODO generalize to always be in the middle bottom of screen
// make the player focusable and set it to be the current focus
player->setFlag(QGraphicsItem::ItemIsFocusable);
player->setFocus();
// add the player to the scene
scene->addItem(player);
// create the score/health
score = new Score();
scene->addItem(score);
health = new Health();
health->setPos(health->x(),health->y()+25);
scene->addItem(health);
level = new Level();
scene->addItem(level);Bull
level->setPos(level->x(),level->y()+50);
// spawn enemies
QTimer * timer = new QTimer();
QObject::connect(timer,SIGNAL(timeout()),player,SLOT(spawn()));
timer->start(2000);
// play background music
QMediaPlayer * music = new QMediaPlayer();
music->setMedia(QUrl("qrc:/sounds/bgsound.mp3"));
music->play();
show();
}
int Game::end(){
if (health == 0){
QApplication::quit();
}
return 0;
}
Health.h
#ifndef HEALTH_H
#define HEALTH_H
#include <QGraphicsTextItem>
class Health: public QGraphicsTextItem{
public:
Health(QGraphicsItem * parent=0);
void decrease();
int getHealth();
private:
int health;
};
#endif // HEALTH_H
Health.cpp
#include "Health.h"
#include <QFont>
#include <QApplication>
Health::Health(QGraphicsItem *parent): QGraphicsTextItem(parent){
// initialize the score to 0
health = 3;
// draw the text
setPlainText(QString("Health: ") + QString::number(health)); // Health: 3
setDefaultTextColor(Qt::red);
setFont(QFont("times",16));
}
void Health::decrease(){
health--;
setPlainText(QString("Health: ") + QString::number(health)); // Health: 2
}
int Health::getHealth(){
return health;
}
main.cpp
#include <QApplication>
#include "Game.h"
#include "Main.h"
Game * game;
int main(int argc, char *argv[]){
QApplication a(argc, argv);
game = new Game();
game->show();
return a.exec();
}

Answer 1

Your end() function is never called.
The best way to achieve what you want to is to use Qt's signal/slot mechanism. It amkes it easy to connect an event (signal) to an action (slot):
Add Q_OBJECT macro to Health and Game classes and make sure your compilation environment moc's the two header files
Declare in Health a signal named dead()
Emit the signal from Health::decrease()
Make Game::end() be a slot and be void
Connect Health::dead() to Game::end()
Then, Game::end() will be called as soon as Health reaches zero.
class Health: public QGraphicsTextItem
{
Q_OBJECT
public:
Health(QGraphicsItem * parent=0);
void decrease();
int getHealth();
signals:
void dead();
private:
int health;
};
...
class Game: public QGraphicsView{
Q_OBJECT
public:
...
public slots:
void end();
};
...
void Health::decrease(){
health--;
setPlainText(QString("Health: ") + QString::number(health));
if ( health == 0 )
emit dead();
}
...
Game::Game(QWidget *parent){
...
connect( health, SIGNAL(dead()), this, SLOT(end()) );
}
...
void Game::end(){
// no need to test health anymore, as signal is emited when health is zero
// do some extra stuff before exiting
QApplication::quit();
}
If end() only calls QApplication::quit(), you can remove it and diectly connect the signal to QApplication::quit(), like that:
connect( health, SIGNAL(dead()), qApp, SLOT(quit()) );
Also note that you were testing health == 0 in Game::end(), but health is a pointer, and, looking at your code, it will never be 0 (you maybe meant to write if ( health->getHealth() == 0 ).

Answer 2

In Health::decrease emit a signal or put the logic for it in where the "player is shot" area. But to do that, you to Health or the class with the logic to be a QObject so that it gets the signals and slots in the header. EDIT QGraphicsTextItem is already a QObject. See comments.
Connect the signal to the view's close() right after the Health class or Player class is instantiated.
http://doc.qt.io/qt-5/signalsandslots.html
Hope that helps.