C++ Qt simple GUI game

Question

I'm trying to learn how to use Qt (5.11.1) for GUI applications so I've done a simple memory game where 12 tiles are displayed and every time the user clicks on a tile it will show an image, so they have to match them into 6 pairs of images.

There's a countdown of 1 minute. Game ends if the time is up before all 6 pairs have been matched, or if all 6 pairs are matched, only that it will show different messages to the user. There is no next level, saving score or anything, so it's very simple.

I know there's room for adding many more features, but would like to know what can be improved from what I've done so far.

My mainwindow.h file:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTimer>
#include <QTime>
#include <QString>
#include <QVector>
#include <QHash>
#include <QRandomGenerator>
#include <QPushButton>
#include <QMessageBox>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow{
    Q_OBJECT


public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    QTimer *timer=new QTimer();
    QTime time;
    QVector<QString> tiles{"tile01", "tile02", "tile03", "tile04",
                              "tile05", "tile06", "tile07", "tile08",
                              "tile09", "tile10", "tile11", "tile12"};
    QHash<QString, QString> tile_image;
    int score=0;
    bool isTurnStarted;
    QPushButton* previousTile;
    QPushButton* currentTile;
    int matchesLeft;
    QMessageBox msgBox;


private slots:
    void updateCountdown();
    void tileCliked();
    void randomize(QVector<QString> &tiles);
    void bindTileImage(QVector<QString> &tiles, QHash<QString, QString> &tile_image);
    void findTurnResult();
    void restartTiles();
    void showImage();
    void findFinalResult();
    void updateState();
    void initalizeGame();


private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

My mainwindow.cpp file:

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    //Connect timer to the slot that will handle the timer
    connect(timer, SIGNAL(timeout()), this, SLOT(updateState()));

    //Connect each button to the same slot, which will figure out which button was pressed and show its associated image file accordingly
    connect(ui->tiles01, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles02, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles03, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles04, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles05, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles06, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles07, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles08, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles09, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles10, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles11, SIGNAL(clicked()), this, SLOT(tileCliked()));
    connect(ui->tiles12, SIGNAL(clicked()), this, SLOT(tileCliked()));

    initalizeGame();
}


void MainWindow::tileCliked(){
    //get the tile that was clicked
    currentTile=qobject_cast<QPushButton*>(sender());

    //get the image linked to that tile in the map and set tile background to it
    showImage();

    //disable current tile so it can't be clicked again (unless there is no match, in which case it will be re-enabled)
    currentTile->setEnabled(false);

    //do something depending on whether the revealed tile is the first or the second tile in the turn
    if (!isTurnStarted){
        previousTile=currentTile;
        isTurnStarted=true;
    }
    else{
        //change score and display it
        findTurnResult();
        ui->lblScore->setText(QString::number(score));

        //reset turn
        isTurnStarted=false;
    }
}


void MainWindow::showImage(){
    QString tile_name=currentTile->objectName();
    QString img=tile_image[tile_name];
    currentTile->setStyleSheet("#" + tile_name + "{ background-image: url(://" + img + ") }");
}


void MainWindow::restartTiles(){
    //return tiles from current turn to the default state (remove backgrounds)
    previousTile->setStyleSheet("#" + previousTile->objectName() + "{ }");
    currentTile->setStyleSheet("#" + currentTile->objectName() + "{ }");

    //re-enable both tiles so they can be used on another turn
    currentTile->setEnabled(true);
    previousTile->setEnabled(true);

    //re-enable the whole tile section
    ui->frame->setEnabled(true);
}


void MainWindow::findFinalResult(){
    msgBox.setWindowTitle("Game has ended");
    msgBox.setIcon(QMessageBox::Information);
    msgBox.setStandardButtons(QMessageBox::Yes);
    msgBox.addButton(QMessageBox::No);
    msgBox.setDefaultButton(QMessageBox::Yes);
    msgBox.setEscapeButton(QMessageBox::No);

    if (matchesLeft==0){
        timer->stop();
        msgBox.setText("Good job! Final score: " + QString::number(score) + "\nPlay again?");
        if (QMessageBox::Yes == msgBox.exec()){
            initalizeGame();
        }
        else{
            QCoreApplication::quit();
        }
    }
    else{
        if (time.toString()=="00:00:00"){
            timer->stop();
            ui->frame->setEnabled(false);
            msgBox.setText("Game over.\nPlay again?");
            if (QMessageBox::Yes == msgBox.exec()){
                initalizeGame();
            }
            else{
                QCoreApplication::quit();
            }
        }
    }
}


void MainWindow::findTurnResult(){
    //check if there is a match (the current tile matches the previous tile in the turn)
    if (tile_image[currentTile->objectName()]==tile_image[previousTile->objectName()]){
        score+=15;
        matchesLeft--;

        //if there is a match, find out if all tiles have been matched.
        findFinalResult();
    }
    else{
        score-=5;

        //disable the whole tile section so no tiles can be turned during the 1-second "memorizing period"
        ui->frame->setEnabled(false);

        //if there is no match, let user memorize tiles and after 1 second hide tiles from current turn so they can be used on another turn
        QTimer::singleShot(1000, this, SLOT(restartTiles()));   
    }
}

void MainWindow::initalizeGame(){
    //start turn
    isTurnStarted=false;

    //Set score
    score=0;
    ui->lblScore->setText(QString::number(score));;

    //Set matches counter
    matchesLeft=6;

    //Set clock for countdown
    time.setHMS(0,1,0);

    //Initialize countdown
    ui->countdown->setText(time.toString("m:ss"));

    // Start timer with a value of 1000 milliseconds, indicating that it will time out every second.
    timer->start(1000);

    //Randomly sort tiles in container
    randomize(tiles);

    //Grab pairs of tiles and bind the name of an image file to each pair
    bindTileImage(tiles, tile_image);

    //enable tiles frame
    ui->frame->setEnabled(true);

    //enable every tile and reset its image
    QList<QPushButton *> btns =  ui->centralWidget->findChildren<QPushButton*>();
    foreach (QPushButton* b, btns) {
        b->setEnabled(true);
        b->setStyleSheet("#" + b->objectName() + "{ }");
    }
}


void MainWindow::updateCountdown(){
    time=time.addSecs(-1);
    ui->countdown->setText(time.toString("m:ss"));
}


void MainWindow::updateState(){
    updateCountdown();
    findFinalResult();
}


void MainWindow::randomize(QVector<QString> &tiles){
    int a,b,min,max;
    min = 0;
    max = tiles.size()-1;
    for(int i=0; i<tiles.size(); i++){
        a=QRandomGenerator::global()->generate() % ((max + 1) - min) + min;
        b=QRandomGenerator::global()->generate() % ((max + 1) - min) + min;
        std::swap(tiles[a],tiles[b]);
    }
}


void MainWindow::bindTileImage(QVector<QString> &tiles, QHash<QString, QString> &tile_image){
    auto iter=tiles.begin();
    for (int i=1; i<=6; i++){
        QString file_name="0"+QString::number(i)+".png";
        tile_image[(*iter)]=file_name;
        iter++;
        tile_image[(*iter)]=file_name;
        iter++;
    }
}


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

And the mainwindow.ui file:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Memory game</string>
  </property>
  <property name="styleSheet">
   <string notr="true">#centralWidget {
background-image: url(://background.png);
}

#howToPlay {
color: white;
}

#countdown {
color: white;
}

#scoring {
color: white;
}

#lblScore {
qproperty-alignment: AlignCenter;
color: white;
background: teal;
border: 3px solid silver;
border-radius: 7px;
}</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QLabel" name="howToPlay">
    <property name="geometry">
     <rect>
      <x>160</x>
      <y>40</y>
      <width>471</width>
      <height>31</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>14</pointsize>
      <weight>75</weight>
      <bold>true</bold>
     </font>
    </property>
    <property name="text">
     <string>Click on two tiles and try to match the images</string>
    </property>
   </widget>
   <widget class="QLabel" name="countdown">
    <property name="geometry">
     <rect>
      <x>690</x>
      <y>20</y>
      <width>81</width>
      <height>20</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>10</pointsize>
      <weight>75</weight>
      <bold>true</bold>
     </font>
    </property>
    <property name="text">
     <string>cronómetro</string>
    </property>
   </widget>
   <widget class="QLabel" name="scoring">
    <property name="geometry">
     <rect>
      <x>330</x>
      <y>520</y>
      <width>71</width>
      <height>21</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>12</pointsize>
      <weight>75</weight>
      <bold>true</bold>
     </font>
    </property>
    <property name="text">
     <string>Puntos:</string>
    </property>
   </widget>
   <widget class="QLabel" name="lblScore">
    <property name="geometry">
     <rect>
      <x>410</x>
      <y>510</y>
      <width>41</width>
      <height>31</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>14</pointsize>
      <weight>75</weight>
      <bold>true</bold>
     </font>
    </property>
    <property name="text">
     <string>0</string>
    </property>
   </widget>
   <widget class="QFrame" name="frame">
    <property name="geometry">
     <rect>
      <x>70</x>
      <y>80</y>
      <width>661</width>
      <height>431</height>
     </rect>
    </property>
    <property name="frameShape">
     <enum>QFrame::StyledPanel</enum>
    </property>
    <property name="frameShadow">
     <enum>QFrame::Raised</enum>
    </property>
    <widget class="QPushButton" name="tile10">
     <property name="geometry">
      <rect>
       <x>180</x>
       <y>300</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile05">
     <property name="geometry">
      <rect>
       <x>20</x>
       <y>160</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile06">
     <property name="geometry">
      <rect>
       <x>180</x>
       <y>160</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile09">
     <property name="geometry">
      <rect>
       <x>20</x>
       <y>300</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile07">
     <property name="geometry">
      <rect>
       <x>340</x>
       <y>160</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile03">
     <property name="geometry">
      <rect>
       <x>340</x>
       <y>20</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile11">
     <property name="geometry">
      <rect>
       <x>340</x>
       <y>300</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile01">
     <property name="geometry">
      <rect>
       <x>20</x>
       <y>20</y>
       <width>130</width>
       <height>110</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile04">
     <property name="geometry">
      <rect>
       <x>500</x>
       <y>20</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile12">
     <property name="geometry">
      <rect>
       <x>500</x>
       <y>300</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile02">
     <property name="geometry">
      <rect>
       <x>180</x>
       <y>20</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
    <widget class="QPushButton" name="tile08">
     <property name="geometry">
      <rect>
       <x>500</x>
       <y>160</y>
       <width>131</width>
       <height>111</height>
      </rect>
     </property>
     <property name="text">
      <string/>
     </property>
    </widget>
   </widget>
   <zorder>frame</zorder>
   <zorder>howToPlay</zorder>
   <zorder>countdown</zorder>
   <zorder>score</zorder>
   <zorder>lblScore</zorder>
  </widget>
  <widget class="QToolBar" name="mainToolBar">
   <attribute name="toolBarArea">
    <enum>TopToolBarArea</enum>
   </attribute>
   <attribute name="toolBarBreak">
    <bool>false</bool>
   </attribute>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

Please note I translated variable and slot names into English for better understanding. I could have missed something.

Thanks!!

ratchet freak · Accepted Answer · 2019-01-10 16:02:31Z

When dealing with Qt 5+ prefer the new connect syntax:

QObject::connect(ui->tiles01, &QPushButton::clicked, this, &MainWindow::tileCliked);

Instead of using sender() in the slot you can use a functor to pass the sender along:

QObject::connect(ui->tiles01, &QPushButton::clicked, this, [=](){tileCliked(ui->tiles01)});

Then tileCliked becomes

void MainWindow::tileCliked(QPushButton* sender){
    //...
}

You shuffle isn't a proper shuffle. Instead you want to do a fisher-yates shuffle:

void MainWindow::randomize(QVector<QString> &tiles){
    int a,b,min,max;
    max = tiles.size()-1;
    for(int i=0; i<tiles.size(); i++){
        min = i;
        a = i;
        b = QRandomGenerator::global()->generate() % ((max + 1) - min) + min;
        if(b != a)
            std::swap(tiles[i],tiles[b]);
    }
}

Any reason not to simply use std::shuffle(), and avoid re-implementing it entirely? — Toby Speight, Jan 10 at 16:07
Not sure why I didn't use std::shuffle()... Would this be a better approach for my randomize() slot?: unsigned seed = std::chrono::system_clock::now().time_since_epoch().count(); shuffle (tiles.begin(), tiles.end(), std::default_random_engine(seed)); — Floella, Jan 10 at 19:43

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