added basic single instance support

examples/mvvmcore/SampleCore/tabviewmodel.h

@@ -7,6 +7,8 @@ class TabViewModel : public QtMvvm::ViewModel
 {
 	Q_OBJECT
 
+	QTMVVM_SINGLETON
+
 public:
 	Q_INVOKABLE explicit TabViewModel(QObject *parent = nullptr);
 	~TabViewModel();

src/imports/mvvmcore/plugins.qmltypes

@@ -587,6 +587,7 @@ Module {
             name: "resultReady"
             Parameter { name: "result"; type: "QVariant" }
         }
+        Signal { name: "instanceInvoked"; revision: 1 }
         Method {
             name: "onInit"
             Parameter { name: "params"; type: "QVariantHash" }

src/mvvmcore/coreapp.cpp

@@ -6,6 +6,7 @@
 
 #include <QtCore/QCommandLineParser>
 #include <QtCore/QRegularExpression>
+#include <QtCore/QMetaClassInfo>
 
 #include <QtGui/QGuiApplication>
 
@@ -41,6 +42,7 @@ void CoreApp::registerApp()
 	qRegisterMetaType<QtMvvm::SettingsElements::Setup>();
 
 	registerInterfaceConverter<IPresenter>();
+
 	//setup
 	setParent(qApp);
 	CoreAppPrivate::instance = this;
@@ -171,6 +173,24 @@ QScopedPointer<CoreAppPrivate> &CoreAppPrivate::dInstance()
 void CoreAppPrivate::showViewModel(const QMetaObject *metaObject, const QVariantHash &params, QPointer<ViewModel> parent, quint32 requestCode)
 {
 	if(presenter) {
+		//first: check for single instance
+		auto isSingleton = false;
+		auto sInfoIndex = metaObject->indexOfClassInfo("qtmvvm_singleton");
+		if(sInfoIndex != -1) {
+			auto sInfo = metaObject->classInfo(sInfoIndex);
+			Q_ASSERT(qstrcmp(sInfo.name(), "qtmvvm_singleton") == 0);
+			isSingleton = qstrcmp(sInfo.value(), "true") == 0;
+		}
+
+		// next handle the singleton
+		if(isSingleton) {
+			auto viewModel = singleInstances.value(metaObject);
+			if(viewModel) {
+				emit viewModel->instanceInvoked(ViewModel::QPrivateSignal{});
+				return;
+			}
+		}
+
 		QPointer<ViewModel> vm;
 		try {
 			auto obj = ServiceRegistry::instance()->constructInjected(metaObject);
@@ -188,6 +208,10 @@ void CoreAppPrivate::showViewModel(const QMetaObject *metaObject, const QVariant
 				});
 			}
 			logDebug() << "Successfully presented" << metaObject->className();
+
+			// if singleton -> store it
+			if(isSingleton)
+				singleInstances.insert(metaObject, vm);
 		} catch(QException &e) {
 			logCritical() << "Failed to present viewmodel of type"
 						  << metaObject->className()

src/mvvmcore/coreapp_p.h

@@ -28,6 +28,7 @@ private:
 	static QPointer<CoreApp> instance;
 
 	IPresenter *presenter = nullptr;
+	QHash<const QMetaObject*, QPointer<ViewModel>> singleInstances;
 };
 
 }

src/mvvmcore/viewmodel.h

@@ -14,6 +14,7 @@
 namespace QtMvvm {
 
 class CoreApp;
+class CoreAppPrivate;
 
 class ViewModelPrivate;
 //! The base class for all viewmodels
@@ -36,6 +37,8 @@ Q_SIGNALS:
 	//! Should be emitted when the viewmodels result is ready
 	void resultReady(const QVariant &result);
 
+	Q_REVISION(1) void instanceInvoked(QPrivateSignal);
+
 protected:
 	//! Show another viewmodel as a child of this one
 	template <typename TViewModel>
@@ -54,12 +57,16 @@ protected:
 
 private:
 	friend class QtMvvm::CoreApp;
+	friend class QtMvvm::CoreAppPrivate;
 
 	QScopedPointer<ViewModelPrivate> d;
 
 	static void showImp(const QMetaObject *metaObject, QVariantHash params, QPointer<ViewModel> parent, quint32 requestCode = 0);
 };
 
+//TODO doc
+#define QTMVVM_SINGLETON Q_CLASSINFO("qtmvvm_singleton", "true")
+
 // ------------- Generic Implementation -------------
 
 template<typename TViewModel>