In my MainWindow there is a button that opens the MbulbWindow. There one can change some parameters and click a Generate button which calls the generateMBulb() function which does some calculation and in the end creates an object named entity of the class internalEntity.

Now I want to "send" this entity to the MainWindow where it will be saved for later use. But how do I do that? My idea was to create the transferEntity(internalEntity& entity) signal and connect it to the addEntity(internalEntity& entity) function of the MainWindow but Qt always gives an error message similar to the following:

Qt Code: 
  1. QObject::connect: No such signal MbulbWindow::MBulbWindow::transferEntity() in ../MandelbulbUI_rewrite/mainwindow.cpp:15
  2.     QObject::connect:  (sender name:   'MbulbWindow')
  3.     QObject::connect:  (receiver name: 'MainWindow')
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Here are my files:

mainwindow.h:

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2.     #define MAINWINDOW_H
  3.  
  4.     #include <QMainWindow>
  5.     #include <QWindow>
  6.     #include <QAction>
  7.     #include "mbulbwindow.h"
  8.     #include "internalentityhandler.h"
  9.  
  10.     QT_BEGIN_NAMESPACE
  11.     namespace Ui { class MainWindow; }
  12.     QT_END_NAMESPACE
  13.  
  14.     class MainWindow : public QMainWindow
  15.     {
  16.         Q_OBJECT
  17.  
  18.     public:
  19.         MainWindow(QWidget *parent = nullptr);
  20.         ~MainWindow();
  21.  
  22.     private:
  23.         Ui::MainWindow *ui;
  24.         internalEntityHandler entityHandler; //Saves and manages entities
  25.         MbulbWindow *mBulbWindow = new MbulbWindow;
  26.     private slots:
  27.  
  28.         //...
  29.  
  30.         //Generate
  31.         void showMBGenerator();
  32.  
  33.         //internal entity management
  34.         void addEntity(internalEntity& entity);
  35.  
  36.     };
  37.     #endif // MAINWINDOW_H
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mainwindow.cpp:

Qt Code: 
  1. #include "mainwindow.h"
  2.     #include "ui_mainwindow.h"
  3.  
  4.     MainWindow::MainWindow(QWidget *parent)
  5.         : QMainWindow(parent)
  6.         , ui(new Ui::MainWindow)
  7.     {
  8.         ui->setupUi(this);
  9.  
  10.         //...
  11.  
  12.         //Connections
  13.         internalEntity entity;
  14.         connect(mBulbWindow, SIGNAL(MBulbWindow::transferEntity()), this, SLOT(addEntity()));
  15.         //This is where I would make the connection
  16.     }
  17.  
  18.     MainWindow::~MainWindow()
  19.     {
  20.         delete ui;
  21.     }
  22.  
  23.     //...
  24.  
  25.     //Generate
  26.     void MainWindow::showMBGenerator(){
  27.         mBulbWindow->show();
  28.     }
  29.  
  30.     //internal entity management
  31.     void MainWindow::addEntity(internalEntity& entity){
  32.         //Entity in memory:
  33.         entityHandler.addEntity(entity);
  34.  
  35.         //...
  36.     }
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mbulbwindow.h:

Qt Code: 
  1. #ifndef MBULBWINDOW_H
  2.     #define MBULBWINDOW_H
  3.  
  4.     #include <QDialog>
  5.     #include <vector>
  6.     #include "boolcloud.h"
  7.     #include "internalentityhandler.h"
  8.  
  9.     namespace Ui {
  10.     class MbulbWindow;
  11.     }
  12.  
  13.     class MbulbWindow : public QDialog
  14.     {
  15.         Q_OBJECT
  16.  
  17.     public:
  18.         explicit MbulbWindow(QWidget *parent = nullptr);
  19.         ~MbulbWindow();
  20.  
  21.     private:
  22.         Ui::MbulbWindow *ui;
  23.  
  24.     private slots:
  25.         void generateMBulb();
  26.     signals:
  27.         void transferEntity(internalEntity& entity);
  28.     };
  29.  
  30.     #endif // MBULBWINDOW_H
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mbulbwindow.cpp:

Qt Code: 
  1. #include "mbulbwindow.h"
  2.     #include "ui_mbulbwindow.h"
  3.  
  4.     MbulbWindow::MbulbWindow(QWidget *parent) :
  5.         QDialog(parent),
  6.         ui(new Ui::MbulbWindow)
  7.     {
  8.         ui->setupUi(this);
  9.  
  10.         //Connections
  11.         connect(ui->ButtonGenerate, SIGNAL(clicked()), this, SLOT(generateMBulb()));
  12.  
  13.     }
  14.  
  15.     MbulbWindow::~MbulbWindow()
  16.     {
  17.         delete ui;
  18.     }
  19.  
  20.     void MbulbWindow::generateMBulb(){
  21.  
  22.         //Calculation of "mBulb" object...
  23.  
  24.         //Create entity
  25.         internalEntity entity(mBulb, "Mandelbulb");
  26.  
  27.         emit transferEntity(entity);
  28.         //This entity needs to be transferred to the MainWindow
  29.         this->close();
  30.     }
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