Qt Signal slot in plugin Architecture

Question

I am trying to Create an Application having a Menu Button. on Clicking the button, a form will be appeared. The Form is created using plugin. The issue is- on first click, one form is generated as normal. But on second click 2 more forms generated instead of one. 3rd click gives 3 more forms and so on. I need only one form with each click.

        Is this has anything to do with Q_PLUGIN_METADATA(IID "Camel1") in interface?

This is My Application Mainwindow.cpp

        spPlugin *objSpPlugin=new spPlugin;

            QSqlQuery qryPlugin=objSpPlugin->view_Plugin_Path(this,publicVariables::inEmployeeId,strFormName,evt::onLoad,true);

            while(qryPlugin.next())
            {


                QString   

    strPluginPath=qryPlugin.value("Plugin_Path").toString();
                qDebug()<<strPluginPath;
                QDir pluginsDir(QDir::currentPath()+"/Plugin");

                QPluginLoader loader(pluginsDir.absoluteFilePath(strPluginPath));

                qDebug()<<loader.fileName();

                QObject *obj=loader.instance();
                qDebug()<<loader.errorString();
                if(obj)
                {

                    MainwindowInterface *objMainWindowInterface=qobject_cast<MainwindowInterface *>(obj);

                    if(objMainWindowInterface)
                    {
                      connect(objMainWindowInterface,SIGNAL(CreateNewFormInstance(QWidget*)),SLOT(createNewFormInstance(QWidget*)));

                        objMainWindowInterface->run();


                    }

                }

            }



        void MainWindow::createNewFormInstance(QWidget*frmInstance)
        {

            qDebug()<<"createNewFormInstance";

                if( frmInstance!=NULL)
                {

                    //
                }
                else
                {

                    ui->mdiArea->addSubWindow(frmInstance);
                }
        }


        My plugin InterFace included in pluginproduct.h

        //#ifndef PLUGININTERFACE_H
        //#define PLUGININTERFACE_H

        //#include<QObject>
        //#include<QWidget>
        //#include<QtSql/QSqlQuery>
        //#include<qsqldatabase.h>


        class FormInterface:public QObject
        {

            Q_OBJECT
        public:
            virtual void Show()=0;

        };





        Q_DECLARE_INTERFACE(MainwindowInterface,"Cam1")


        //#endif // PLUGININTERFACE_H




   My Pluginproduct.h 


        class  LibPluginProductForm:public FormInterface

        {


           Q_OBJECT
           Q_PLUGIN_METADATA(IID "Camel1")
           Q_INTERFACES(FormInterface)



        public:
            LibPluginProductForm();

            ~ LibPluginProductForm();
            void Show();


        private:

            QWidget *frm;


        };


        my pluginProduct.cpp


        LibPluginProductForm::LibPluginProductForm()

        {


         frm=new QWidget;



        }

        LibPluginProductForm::~LibPluginProductForm()
        {


        }

        void LibPluginProductForm::Show()

        {


            emit CreateNewFormInstance(frm);
            qDebug()<<"LibPluginProductForm::Show";


            frm->show();`enter code here`

        }

Answer 1

The signal will be raised when the 'CreaeNewFormInstance' is called but also from LibPluginProduceForm::Show where you are manually 'emitting' the signal.

Check that your 'Show' method is not being called multiple times. Are you seeing your debug statement in the Application Output ?