[SOLVED] Simple QT Question: Connecting Widgets to Slots

tony5429 · 2009-05-27 21:24:11

Thanks for your tips. I'd like to try option #1... so I've got this now,

//run sendEmail() when item8 is clicked
QObject::connect(item8, SIGNAL(clicked()), signalMapper, SLOT(map()));
signalMapper->setMapping(item8, item3);
QObject::connect(signalMapper, SIGNAL(mapped(QString)), composerInstance, SLOT(sendEmail(QString)));

What are you saying exactly about the last line there?

scio · 2009-05-27 22:00:42

change it to

QObject::connect(signalMapper, SIGNAL(mapped(QWidget*)), composerInstance, SLOT(sendEmail(QWidget*)));

then in sendEmail do something like:

void sendEmail(QWidget *textBox) {
            QLineEdit *lineEdit = qobject_cast<QLineEdit*>(textBox);
            QString address = (lineEdit)? lineEdit->text() : "";
            QString printOut = QString("echo \"sending email to %1\"").arg(address);
            system(printOut.toUtf8());
        }

I did not have time to test this, but I think it will work.

tony5429 · 2009-05-28 04:06:36

Thanks! That works, although, unfortunately I do not see how I can pass more than one QWidget to sendEmail()... Is there a way? It seems setMapping will only let me map one QWidget at a time...

scio · 2009-05-28 13:26:33

QSignalMapper also lets you create mappings for QObjects, so just create a class that is a QObject with public pointers to all the widgets you want to reference. Again, not the most elegant, but it should get the job done. I always prefer get it working first, then make it pretty.

Some pseudo-code since that might be easier to understand...

class WidgetContainer : public QObject {
   public:
      WidgetContainer(QWidget *thingOne, QWidget *thingTwo, QWidget *thingThree, QObject *parent = NULL)
         :QObject(parent),
         firstThing(thingOne),
         secondThing(thingTwo),
         thirdThing(thingThree)
      {
      }

      QWidget1 *firstThing;
      QWidget2 *secondThing;
      QWidget3 *thirdThing;
}

signalMapper->setMapping(item8, myWidgetContainer);
QObject::connect(signalMapper, SIGNAL(mapped(QObject*)), composerInstance, SLOT(sendEmail(QObject*)));

void sendEmail(QObject *container) {
            WidgetContainer *widgetContainer = qobject_cast<WidgetContainer*>(container);
            if(widgetContainer) {
               // Do the old sendEmail stuff in here pulling from widgetContainer->firstThing, secondThing, thirdThing etc. when needed.
        }

I realize now that is more C++ than pseudo-code :-P

tony5429 · 2009-05-28 17:59:30

I see the second code section goes in main.cpp and the third goes in emailcomposer.h. Where does the first go? I have tried it in emailcomposer.h, but without luck,

#ifndef EMAILCOMPOSER_H
#define EMAILCOMPOSER_H

#include <QtGui>
#include <cstdlib>

class EmailComposer : public QObject {
    Q_OBJECT

    public:
        EmailComposer() {}

    public slots:
        void sendEmail(QWidget *textBox) {
            QTextEdit *textEdit = qobject_cast<QTextEdit*>(textBox);
            system(QString("echo \"sending email to %1\"").arg((textEdit)? (textEdit)->toPlainText() : "").toUtf8());
        }
};

class WidgetContainer : public QObject {
    Q_OBJECT

    public:
        WidgetContainer(QWidget *thingOne, QWidget *thingTwo, QObject *parent = NULL) : QObject(parent), QLineEdit(thingOne), QTextEdit(thingTwo) {
            QLineEdit *firstThing;
            QTextEdit *secondThing;
        }
};

#endif

Here is the error I get when I try to compile:

./emailcomposer.h: In constructor 'WidgetContainer::WidgetContainer(QWidget*, QWidget*, QObject*)':
./emailcomposer.h:24: error: type 'QLineEdit' is not a direct base of 'WidgetContainer'
./emailcomposer.h:24: error: type 'QTextEdit' is not a direct base of 'WidgetContainer'

scio · 2009-05-28 22:29:58

Double check your code, it looks like you didn't copy the WidgetContainer class correctly. Specifically your initializer list.

tony5429 · 2009-05-28 22:52:46

Yeah; I was a little unsure about the proper usage of that code. I think I am doing it closer to correct now, but I am still having an issue. It seems I cannot make a widget container inside the header file because the definition of the widget container is also in that header file...

emailcomposer.h,

#ifndef EMAILCOMPOSER_H
#define EMAILCOMPOSER_H

#include <QtGui>
#include <cstdlib>

class EmailComposer : public QObject {
    Q_OBJECT

    public:
        EmailComposer() {}

    public slots:
        void sendEmail(QObject *container) {
            WidgetContainer *widgetContainer = qobject_cast<WidgetContainer*>(container);
            if (widgetContainer) {
                QTextEdit *textEdit = qobject_cast<QTextEdit*>(widgetContainer->firstThing());
                system(QString("echo \"sending email to %1\"").arg((textEdit)? (textEdit)->toPlainText() : "").toUtf8());
            }
        }
};

class WidgetContainer : public QObject {
    Q_OBJECT

   public:
      WidgetContainer(QWidget *thingOne, QWidget *thingTwo, QObject *parent = NULL)
         :QObject(parent),
         firstThing(thingOne),
         secondThing(thingTwo)
      {
      }

      QWidget *firstThing;
      QWidget *secondThing;
};

#endif

main.cpp,

#include <QtGui>
#include <emailcomposer.h>

int main(int argc, char *argv[]) {

    //define qapplication class
    QApplication app(argc, argv);

    //create an instance of the email composer
    EmailComposer *composerInstance = new EmailComposer;

    //create qt widgets and signal mappers
    QWidget *window = new QWidget;
    QSignalMapper *signalMapper = new QSignalMapper(window);
    QLabel *item1 = new QLabel("Status: ready...");
    QLabel *item2 = new QLabel("Name:");
    QLineEdit *item3 = new QLineEdit("put the name here!");
    QLabel *item4 = new QLabel("Options:");
    QComboBox *item5 = new QComboBox();
    item5->insertItem(0, "a");
    item5->insertItem(1, "b");
    item5->insertItem(2, "c");
    QLabel *item6 = new QLabel("begin!");
    QTextEdit *item7 = new QTextEdit();
    QPushButton *item8 = new QPushButton("Send");

    //create WidgetContainer
    WidgetContainer *myWidgetContainer = new WidgetContainer(item3, item7);

    //run sendEmail() when item8 is clicked
    QObject::connect(item8, SIGNAL(clicked()), signalMapper, SLOT(map()));
    signalMapper->setMapping(item8, myWidgetContainer);
    QObject::connect(signalMapper, SIGNAL(mapped(QObject*)), composerInstance, SLOT(sendEmail(QObject*)));

    //create layout and add widgets to layout
    QGridLayout *layout = new QGridLayout;
    layout->addWidget(item1, 0, 0, 1, 2);
    layout->addWidget(item2, 2, 0);
    layout->addWidget(item3, 2, 1);
    layout->addWidget(item4, 3, 0);
    layout->addWidget(item5, 3, 1);
    layout->addWidget(item6, 4, 0, 1, 2);
    layout->addWidget(item7, 5, 0, 1, 2);
    layout->addWidget(item8, 6, 0, 1, 2);

    //output to screen
    window->setLayout(layout);
    window->show();

    //pass control to qt
    return app.exec();
}

The error,

[karam@boris emailcomposer]$ qmake -project
[karam@boris emailcomposer]$ qmake
[karam@boris emailcomposer]$ make
g++ -c -m64 -pipe -march=x86-64 -mtune=generic -O2 -pipe -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt/mkspecs/linux-g++-64 -I. -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include -I. -I. -I. -I. -o main.o main.cpp
In file included from main.cpp:2:
./emailcomposer.h: In member function 'void EmailComposer::sendEmail(QObject*)':
./emailcomposer.h:15: error: 'WidgetContainer' was not declared in this scope
./emailcomposer.h:15: error: 'widgetContainer' was not declared in this scope
./emailcomposer.h:15: error: 'WidgetContainer' cannot appear in a constant-expression
./emailcomposer.h:15: error: parse error in template argument list
./emailcomposer.h:15: error: no matching function for call to 'qobject_cast(QObject*&)'
make: *** [main.o] Error 1
[karam@boris emailcomposer]$

scio · 2009-05-29 13:16:25

Try this:

emailcomposer.h

#ifndef EMAILCOMPOSER_H
#define EMAILCOMPOSER_H

#include <QtGui>
#include <cstdlib>

class WidgetContainer : public QObject {
    Q_OBJECT

   public:
      WidgetContainer(QWidget *thingOne, QWidget *thingTwo, QObject *parent = NULL)
         :QObject(parent),
         firstThing(thingOne),
         secondThing(thingTwo)
      {
      }

      QWidget *firstThing;
      QWidget *secondThing;
};


class EmailComposer : public QObject {
    Q_OBJECT

    public:
        EmailComposer() {}

    public slots:
        void sendEmail(QObject *container) {
            WidgetContainer *widgetContainer = qobject_cast<WidgetContainer*>(container);
            if (widgetContainer) {
                QTextEdit *textEdit = qobject_cast<QTextEdit*>(widgetContainer->firstThing());
                system(QString("echo \"sending email to %1\"").arg((textEdit)? (textEdit)->toPlainText() : "").toUtf8());
            }
        }
};
#endif

tony5429 · 2009-05-29 13:55:10

scio: It works perfectly now! I have one last question for you: this little piece of code is actually part of an open-source package I'm planning to release next month and I'd like to put you somewhere in the credits. Shall I refer to you as simply 'scio' or is there a full name you'd like to give me? Thanks again for all your help!

scio · 2009-05-29 21:59:03

Adam Weiss is my name, thanks.

tony5429 · 2009-07-02 19:07:01

The code has been released: http://krondi.org

Arch Linux

#26 2009-05-27 21:24:11

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#27 2009-05-27 22:00:42

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#28 2009-05-28 04:06:36

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#29 2009-05-28 13:26:33

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#30 2009-05-28 17:59:30

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#31 2009-05-28 22:29:58

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#32 2009-05-28 22:52:46

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#33 2009-05-29 13:16:25

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#34 2009-05-29 13:55:10

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#35 2009-05-29 21:59:03

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

#36 2009-07-02 19:07:01

Re: [SOLVED] Simple QT Question: Connecting Widgets to Slots

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