(C++) QtExample30

 

 

Qt example 30: controlling program flow with a Singleton is a Qt Example that uses Singleton to produce dialogs until it is told to quit.

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 15.04 (vivid)

IDE(s):

• Qt Creator 3.1.1

Project type:

• GUI application

C++ standard:

• C++11

Compiler(s):

• G++ 4.9.2

Libraries used:

• Qt: version 5.4.1 (32 bit)
• STL: GNU ISO C++ Library, version 4.9.2

 

 

 

 

 

Qt project file: ./CppQtExample30/CppQtExample30.pro

 

---

exists(../../DesktopApplication.pri) {   include(../../DesktopApplication.pri) } !exists(../../DesktopApplication.pri) {   QT += core gui   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets   TEMPLATE = app   CONFIG(debug, debug|release) {     message(Debug mode)   }   CONFIG(release, debug|release) {     message(Release mode)     DEFINES += NDEBUG NTRACE_BILDERBIKKEL   }   QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra   unix {     QMAKE_CXXFLAGS += -Werror   } } exists(../../Libraries/Boost.pri) {   include(../../Libraries/Boost.pri) } !exists(../../Libraries/Boost.pri) {   win32 {     INCLUDEPATH += \       ../../../Projects/Libraries/boost_1_55_0   } } SOURCES += \     main.cpp \     firstdialog.cpp \     seconddialog.cpp \     commander.cpp HEADERS  += \     firstdialog.h \     seconddialog.h \     commander.h FORMS    += \     firstdialog.ui \     seconddialog.ui

 

 

 

 

 

./CppQtExample30/commander.h

 

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#ifndef COMMANDER_H #define COMMANDER_H ///Commander is a Singleton for managing program flow struct Commander {   ///Get the Commander's only instance   static Commander * GetInstance();   ///Start the program   void Run();   ///Child asks to quit the program   void Quit();   private:   ///A Singleton's constructor is private   Commander();   ///The one and only Commander instance   static Commander * m_instance;   ///Flag the tell whether to quit   bool m_quit; }; #endif // COMMANDER_H

 

 

 

 

 

./CppQtExample30/commander.cpp

 

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#include "commander.h" #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <boost/shared_ptr.hpp> #include "firstdialog.h" #include "seconddialog.h" #pragma GCC diagnostic pop Commander * Commander::m_instance = 0; Commander::Commander()   : m_quit(false) { } Commander * Commander::GetInstance() {   if (!m_instance) m_instance = new Commander;   return m_instance; } void Commander::Quit() {   m_quit = true; } void Commander::Run() {   while (!m_quit)   {     boost::shared_ptr<QDialog> dialog(       ((std::rand() >> 4) % 2)       ? dynamic_cast<QDialog*>(new FirstDialog)       : dynamic_cast<QDialog*>(new SecondDialog));     dialog->exec();   } }

 

 

 

 

 

./CppQtExample30/firstdialog.h

 

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#ifndef FIRSTDIALOG_H #define FIRSTDIALOG_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QDialog> #pragma GCC diagnostic pop namespace Ui {   class FirstDialog; } class FirstDialog : public QDialog {   Q_OBJECT      public:   explicit FirstDialog(QWidget *parent = 0);   FirstDialog(const FirstDialog&) = delete;   FirstDialog& operator=(const FirstDialog&) = delete;   ~FirstDialog();      private:   Ui::FirstDialog *ui; }; #endif // FIRSTDIALOG_H

 

 

 

 

 

./CppQtExample30/firstdialog.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include "firstdialog.h" #include "ui_firstdialog.h" #pragma GCC diagnostic pop FirstDialog::FirstDialog(QWidget *parent) :     QDialog(parent),     ui(new Ui::FirstDialog) {     ui->setupUi(this); } FirstDialog::~FirstDialog() {     delete ui; }

 

 

 

 

 

./CppQtExample30/main.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include "commander.h" #include <QApplication> #pragma GCC diagnostic pop int main(int argc, char *argv[]) {   QApplication a(argc, argv);   Commander::GetInstance()->Run();   return 0; }

 

 

 

 

 

./CppQtExample30/seconddialog.h

 

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#ifndef SECONDDIALOG_H #define SECONDDIALOG_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QDialog> #pragma GCC diagnostic pop namespace Ui {   class SecondDialog; } class SecondDialog : public QDialog {   Q_OBJECT      public:   explicit SecondDialog(QWidget *parent = 0);   SecondDialog(const SecondDialog&) = delete;   SecondDialog& operator=(const SecondDialog&) = delete;   ~SecondDialog() noexcept;      private slots:   void on_pushButton_clicked(); private:   Ui::SecondDialog *ui; }; #endif // SECONDDIALOG_H

 

 

 

 

 

./CppQtExample30/seconddialog.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include "seconddialog.h" #include "ui_seconddialog.h" #include "commander.h" #pragma GCC diagnostic pop SecondDialog::SecondDialog(QWidget *parent)   : QDialog(parent),     ui(new Ui::SecondDialog) {     ui->setupUi(this); } SecondDialog::~SecondDialog() noexcept {   delete ui; } void SecondDialog::on_pushButton_clicked() {   Commander::GetInstance()->Quit();   this->close(); }