I can't see what I'm doing wrong. I'm trying to create some properties in a class (as I did before) but this time I'm getting the error "class Foo has no member named MyProp"
The header is:
#ifndef P_H
#define P_H
#include <QObject>
class P : public QObject
{
Q_OBJECT
Q_PROPERTY(int Prop READ getProp WRITE setProp)
public:
explicit P(QObject *parent = 0);
int getProp() const;
void setProp(int nP);
private:
int m_p;
};
#endif // P_H
and the cpp file is:
#include "p.h"
P::P(QObject *parent) :
QObject(parent)
{
}
int P::getProp() const
{
return m_p;
}
void P::setProp(int nP)
{
m_p = nP;
}
But when I try to use foobar.P I got the error class P has no member named P. I've been reading Qt documentation and I can't see any difference. Does anyone see what I'm doing wrong?
I'm using Qt Creator 2.4.1 and Qt 4.8.
[... Edit ...]
Here is how I'm trying to use it:
#include "p.h"
int main(int argc, char *argv[])
{
P c;
c.Prop = 2;
return 0;
}
This is the simplest example I could think of and I got the same error.
Thanks in advance.
You need to use it like this:
P c;
c.setProperty("Prop", 42); // set the property
c.property("Prop"); // retrieve the property
Related
Question: Is there a way to check at compile-time if qRegisterMetaType<T>() was called for a custom type T?
The custom type T needs to be registered in Qt meta-type system in order to be used in e.g. queued connections.
If such a connection is made, and a signal triggered, the runtime warning will be shown:
QObject::connect: Cannot queue arguments of type 'T'
(Make sure 'T' is registered using qRegisterMetaType().)
This is hard to track, so I would prefer to check this at compile-time. Is that in any way possible?
(I understand that if it was possible, it would probably already be a part of Qt Framework itself, but maybe...?)
Note: I know I can check if a type was declared as metatype (Check if type is declared as a meta type system (for SFINAE)), but this doesn't solve my problem.
The code example would be:
#include <QCoreApplication>
#include <QDebug>
#include <QMetaMethod>
#include <QObject>
#include <QThread>
#include <QTimer>
struct Payload {
Payload() = default;
};
// Type is declared as metatype
Q_DECLARE_METATYPE(Payload)
class ObjectOne : public QObject {
Q_OBJECT
public:
using QObject::QObject;
void emitPayloadChanged() { Payload p; emit payloadChanged(p); }
signals:
void payloadChanged(const Payload& p);
};
class ObjectTwo : public QObject {
Q_OBJECT
public:
using QObject::QObject;
void handlePayload(const Payload& p) { qDebug() << "handling payload"; }
};
int main(int argc, char* argv[]) {
QCoreApplication app(argc, argv);
// Uncommenting the following line fixes the runtime warning
// qRegisterMetaType<Payload>();
QThread t1, t2;
ObjectOne o1;
o1.moveToThread(&t1);
ObjectTwo o2;
o2.moveToThread(&t2);
t1.start();
t2.start();
QObject::connect(&o1, &ObjectOne::payloadChanged, &o2, &ObjectTwo::handlePayload);
QTimer::singleShot(0, &o1, [&] { QMetaObject::invokeMethod(&o1, &ObjectOne::emitPayloadChanged); });
return app.exec();
}
#include "main.moc"
I'm trying to use a QDeclarativeListProperty in order to manage a list of parameters, mostly for the purposes of displaying them in a ListView. However, I would also like to be able to directly access the parameters in QML from the QDeclarativeListProperty so that I can display/modify individual parameters on different screens.
My class is called ParameterClass, for which I've created a QList:
class SystemData : public QObject
{
Q_OBJECT
Q_PROPERTY(QDeclarativeListProperty<ParameterClass> parameters READ parameters CONSTANT)
QDeclarativeListProperty<ParameterClass> parameters();
...
QList<ParameterClass *> m_parameterList;
}
I've also registered the ParameterClass class and set up an instance of my SystemData as a property, which I know is necessary.
m_context->setContextProperty("SystemData", m_pSystemData);
qmlRegisterType<ParameterClass>();
Now, what I want to do within QML is something like this:
Rectangle {
id: frame
property variant parameter: SystemData.parameters[5]
...
}
I'm just not getting it to work: I keep getting back [undefined]. Am I wasting my time, or am I missing something?
Edit:
I've changed things to use the suggestion from ... . Here are some selections from my updated code.
main.cpp:
#include <QApplication>
#include <QSplashScreen>
#include <QLocale>
#include <QLibraryInfo>
#include <QDeclarativeView>
#include <QDeclarativeContext>
#include <QDeclarativeEngine>
#include <QObject>
#include <QDeclarativeListProperty>
#include "systemdata.h"
#include "parameterclass.h"
static const QString contentPath = "qrc:/qml/qml/pk_ui/";
static const QString filename(contentPath + "main.qml");
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QDeclarativeView mainView;
SystemData* systemData = SystemData::getInstance();
QThread thread;
UpdateWorker updateWorker;
QObject::connect((const QObject*)systemData, SIGNAL(startWork()),
(const QObject*)&updateWorker, SLOT(doWork()));
updateWorker.moveToThread(&thread);
thread.start();
systemData->startUpdates();
QFont defaultFont;
defaultFont.setFamily("Sans Serif");
QApplication::setFont(defaultFont);
// Register types to be available in QML
qmlRegisterType<ParameterClass>();
qmlRegisterUncreatableType<SystemEnum>("SystemEnums", 1, 0, "SystemEnum", QString());
mainView.engine()->rootContext()->setContextProperty("SystemData", systemData);
// Set view optimizations not already done for QDeclarativeView
mainView.setResizeMode(QDeclarativeView::SizeRootObjectToView);
mainView.setAttribute(Qt::WA_OpaquePaintEvent);
mainView.setAttribute(Qt::WA_NoSystemBackground);
mainView.setSource(QUrl(filename));
mainView.show();
return app.exec();
}
The ParameterClass looks like this:
class ParameterClass : public QObject
{
Q_OBJECT
Q_PROPERTY(int type READ get_type NOTIFY typeChanged)
Q_PROPERTY(bool enabled READ get_ParameterEnabled WRITE set_ParameterEnabled NOTIFY enabledChanged)
Q_PROPERTY(int groupID READ get_GroupID WRITE set_GroupID NOTIFY groupIDChanged)
Q_PROPERTY(int unitID READ get_UnitID WRITE set_UnitID NOTIFY unitIDChanged)
Q_PROPERTY(int securityLevel READ get_SecurityLevel WRITE set_SecurityLevel NOTIFY securityLevelChanged)
Q_PROPERTY(QString parameterName READ get_ParameterName NOTIFY parameterNameChanged)
Q_PROPERTY(QString shortDescription READ get_ShortDescription NOTIFY shortDescriptionChanged)
Q_PROPERTY(int currentValue READ get_CV WRITE set_valueptrvalue NOTIFY currentValueChanged)
Q_PROPERTY(int lowerBound READ get_LB NOTIFY lowerBoundChanged)
Q_PROPERTY(int upperBound READ get_UB NOTIFY upperBoundChanged)
public:
struct ValueTypes
{
enum
{
IntegerType,
StringType,
StringListType
};
};
ParameterClass(QObject *parent = 0);
int get_type();
bool get_ParameterEnabled();
int get_GroupID();
int get_UnitID();
int get_SecurityLevel();
QString get_ParameterName();
QString get_ShortDescription();
int get_CV() { return *CurrentValuePtr; }
int get_LB() { return *LowerBoundPtr; }
int get_UB() { return *UpperBoundPtr; }
void set_ParameterEnabled(bool InParameterEnabled);
void set_GroupID(int InGroupID);
void set_UnitID(int InUnitID);
void set_SecurityLevel(int InSecurityLevel);
signals:
void typeChanged();
void enabledChanged();
void groupIDChanged();
void unitIDChanged();
void securityLevelChanged();
void parameterNameChanged();
void shortDescriptionChanged();
private:
int type;
bool ParameterEnabled;
int GroupID;
int UnitID;
int SecruityLevel;
QString ParameterName;
QString ShortDescription;
int * CurrentValuePtr;
int * LowerBoundPtr;
int * UpperBoundPtr;
};
And my QML file:
Rectangle {
id: frame
property int val: SystemData.parameters[4].currentValue
...
}
It looks like I'm still getting an undefined value in this case. I'm trying to debug now, so that I can provide more information.
It's very much possible. The key is to make sure you register the QML type and set the context property before setting the source on your QDeclarativeView.
Here's a working example -
main.cpp:
#include <QApplication>
#include <QtDeclarative>
class MyPropertyObject : public QObject {
Q_OBJECT
Q_PROPERTY(int value READ value CONSTANT)
public:
MyPropertyObject(int value = -1) : m_value(value) { }
int value() const {
return m_value;
}
private:
int m_value;
};
class MyObject : public QObject {
Q_OBJECT
Q_PROPERTY(QDeclarativeListProperty<MyPropertyObject> props READ props CONSTANT)
public:
MyObject() {
m_props.append(new MyPropertyObject(55));
m_props.append(new MyPropertyObject(44));
m_props.append(new MyPropertyObject(33));
}
QDeclarativeListProperty<MyPropertyObject> props() {
return QDeclarativeListProperty<MyPropertyObject>(this, m_props);
}
private:
QList<MyPropertyObject *> m_props;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDeclarativeView view;
view.engine()->rootContext()->setContextProperty(QLatin1String("tester"), new MyObject);
qmlRegisterType<MyPropertyObject>();
view.setSource(QUrl("qrc:///qml/main.qml"));
view.setResizeMode(QDeclarativeView::SizeRootObjectToView);
view.resize(300, 300);
view.show();
return a.exec();
}
#include "main.moc"
main.qml:
import QtQuick 1.1
Rectangle {
property variant foo: tester.props[2].value
Text {
anchors.centerIn: parent
text: parent.foo
}
}
Note: read the docs for the QDeclarativeListProperty constructors. The one I'm using for this example is not the preferred one, but is good for quick prototypes.
i am playing with Exposing Attributes of C++ Types to QML in Qt5 based on this tutor http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-exposecppattributes.html. when i run it i got this error on my issues pane error: variable 'QQmlComponent component' has initializer but incomplete type not only i have this error i have also this error the signal i have created using Q_PROPERTY is not detected
C:\Users\Tekme\Documents\QtStuf\quick\QmlCpp\message.h:15: error: 'authorChanged' was not declared in this scope
emit authorChanged();
^
my code is
#ifndef MESSAGE_H
#define MESSAGE_H
#include <QObject>
class Message : public QObject
{
Q_OBJECT
Q_PROPERTY(QString author READ author WRITE setAuthor NOTIFY authorChanged)
public:
void setAuthor(const QString &a) {
if (a != m_author) {
m_author = a;
emit authorChanged();
}
}
QString author() const {
return m_author;
}
private:
QString m_author;
};
#endif
and in my main.cpp
#include "message.h"
#include <QApplication>
#include <QQmlEngine>
#include <QQmlContext>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QQmlEngine engine;
Message msg;
engine.rootContext()->setContextProperty("msg",&msg);
QQmlComponent component(&engine, QUrl::fromLocalFile("main.qml"));
component.create();
return a.exec();
}
You are not including QQmlComponent header in your main.cpp:
#include <QQmlComponent>
You are also trying to emit a signal that you haven't declared yet. You should declare it in your message.h like this:
signals:
void authorChanged();
Check this example.
I believe you need to add:
signals:
void authorChanged();
to your class like this:
class Message : public QObject
{
Q_OBJECT
Q_PROPERTY(QString author READ author WRITE setAuthor NOTIFY authorChanged)
public:
void setAuthor(const QString &a) {
if (a != m_author) {
m_author = a;
emit authorChanged();
}
}
QString author() const {
return m_author;
}
signals:
void authorChanged();
private:
QString m_author;
};
I tried declaring a signal in a prototype and then connecting it is script funcition for some reason it does not work as I hoped. My code is as follows. Could some one help me in this.
What I expected was, once I called p.setText('New String') in the script code, since setText emits the textChanged signal it should invoke the slot which is catchSignal(text) already connected in the script code.
Prototype header
#ifndef SCRIPTACTION_H
#define SCRIPTACTION_H
#include <QObject>
#include <QtScript>
class ScriptAction : public QObject , public QScriptable
{
Q_OBJECT
public:
ScriptAction(QObject *parent = 0);
signals:
void textChanged(const QString changedString);
};
#endif // SCRIPTACTION_H
Class
#include "scriptaction.h"
#include <QAction>
Q_DECLARE_METATYPE(QAction*)
ScriptAction::ScriptAction(QObject *parent) : QObject(parent)
{
}
Main Class
#include <QApplication>
#include <QDebug>
#include <QAction>
#include "scriptaction.h"
#include <QPushButton>
Q_DECLARE_METATYPE(QAction*)
QScriptValue qAction_Constructor(QScriptContext *ctx, QScriptEngine *eng)
{
qDebug() << "QAction is called";
if(ctx->isCalledAsConstructor())
{
QObject *parent = ctx->argument(0).toQObject();
QAction *action = new QAction("Test",parent);
return eng->newQObject(action, QScriptEngine::ScriptOwnership);
} else {
return QString("invalid call. Use new Constructor");
}
}
int main(int argc, char *argv[])
{
QApplication app(argc,argv);
QScriptEngine engine;
//Evaluating a simaple expresssion
qDebug() << engine.evaluate("1+2").toNumber();
QPushButton button;
QScriptValue buttonScript= engine.newQObject(&button);
engine.globalObject().setProperty("button", buttonScript);
engine.evaluate("button.text ='Hello Text'; button.show()");
//QAction Prototype
ScriptAction qsAction ;
QScriptValue script_proto = engine.newQObject(&qsAction);
engine.setDefaultPrototype(qMetaTypeId<QAction*>(), script_proto);
QScriptValue ctor = engine.newFunction(qAction_Constructor , script_proto);
QScriptValue metaObject = engine.newQMetaObject(&QObject::staticMetaObject, ctor);
engine.globalObject().setProperty("QSAction" , metaObject);
engine.evaluate("var p = new QSAction(button);p.textChanged.connect(catchSignal);");
engine.evaluate("function catchSignal(text) { print ('PROTOTYPE SIGNAL IS CALLED ',text); } p.setText('New String'); " );
return app.exec();
}
I got rid of the issue, and now I see the signal is being triggered and slot is called properly.
All I did was moving the code to a separate script file and start using the QScriptDebugger to see its output. Then I figured there was an error and the code is edited to work.
Anyone who wants an example prototype class, this will hopefully be a good guideline.
I am working on building a GUI around a console application. I would like to be able to click a button to run the console app and show the console output inside of the GUI itself. How might I accomplish this? I am working in Linux.
You could also try QProcess. It provides a Qt interface to launching external processes, reading their I/O and waiting, or not, on their completion.
For your purpose, it sounds like you want the process to run asynchronously, so code might look like :
myprocessstarter.h :
#include <QObject>
#include <QProcess>
#include <QDebug>
class MyProcessStarter : public QObject
{
Q_OBJECT
public:
MyProcessStarter() : QObject() {};
void StartProcess();
private slots:
void readStandardOutput();
private:
QProcess *myProcess;
};
main.cpp:
#include "myprocessstarter.h"
void MyProcessStarter::StartProcess()
{
QString program = "dir";
QStringList arguments;
// Add any arguments you want to be passed
myProcess = new QProcess(this);
connect(myProcess, SIGNAL(readyReadStandardOutput()), this, SLOT(readStandardOutput()));
myProcess->start(program, arguments);
}
void MyProcessStarter::readStandardOutput()
{
QByteArray processOutput;
processOutput = myProcess->readAllStandardOutput();
qDebug() << "Output was " << QString(processOutput);
}
void main(int argc, char** argv)
{
MyProcessStarter s;
s.StartProcess();
}
I wanted to do something similar in one of my applications. I redirected all output from the standard stream (cout) to my console window. To periodically read out the stream contents I use a timer loop. Works fine for me.
StdRedirector.cpp
#include "StdRedirector.h"
QMutex coutMutex;
void outcallback(const char* ptr, std::streamsize count, void* bufferString)
{
string *b = (string *) bufferString;
string t;
for (int i=0; i < count; i++)
{
if (ptr[i] == '\n')
{
t = t + "\n";
} else {
t = t + ptr[i];
}
}
coutMutex.lock();
*b = *b + t;
coutMutex.unlock();
}
void ConsoleWindow::updateTimer(void)
{
coutMutex.lock();
if (bufferString.size() > 0)
{
consoleBox->insertPlainText(QString(bufferString.c_str()));
bufferString.clear();
QScrollBar *sb = consoleBox->verticalScrollBar();
sb->setValue(sb->maximum());
}
coutMutex.unlock();
}
ConsoleWindow::ConsoleWindow(QWidget *parent) : QWidget(parent)
{
consoleBox = new QTextEdit(this);
consoleBox->setReadOnly(true);
stdRedirector = new StdRedirector<>(std::cout, outcallback, &bufferString);
QVBoxLayout *vb = new QVBoxLayout();
vb->addWidget(consoleBox);
vb->setMargin(0);
vb->setSpacing(0);
setLayout(vb);
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(updateTimer()));
timer->start(100);
}
ConsoleWindow::~ConsoleWindow()
{
delete stdRedirector;
}
StdRedirector.h
#ifndef STD_REDIRECTOR
#define STD_REDIRECTOR
#include <QWidget>
#include <QTextEdit>
#include <QString>
#include <QVBoxLayout>
#include <QTimer.h>
#include <QMutex>
#include <QScrollBar>
#include <iostream>
#include <string>
using namespace std;
template<class Elem = char, class Tr = std::char_traits<Elem>>
class StdRedirector : public std::basic_streambuf<Elem, Tr>
{
typedef void (*pfncb) ( const Elem*, std::streamsize _Count, void* pUsrData );
public:
StdRedirector(std::ostream& a_Stream, pfncb a_Cb, void* a_pUsrData) :
m_Stream(a_Stream),
m_pCbFunc(a_Cb),
m_pUserData(a_pUsrData)
{
m_pBuf = m_Stream.rdbuf(this);
}
~StdRedirector()
{
m_Stream.rdbuf(m_pBuf);
}
std::streamsize xsputn(const Elem* _Ptr, std::streamsize _Count)
{
m_pCbFunc(_Ptr, _Count, m_pUserData);
return _Count;
}
typename Tr::int_type overflow(typename Tr::int_type v)
{
Elem ch = Tr::to_char_type(v);
m_pCbFunc(&ch, 1, m_pUserData);
return Tr::not_eof(v);
}
protected:
std::basic_ostream<Elem, Tr>& m_Stream;
std::streambuf* m_pBuf;
pfncb m_pCbFunc;
void* m_pUserData;
};
class ConsoleWindow : public QWidget
{
Q_OBJECT
public:
ConsoleWindow(QWidget *parent = 0);
~ConsoleWindow();
public slots:
void updateTimer(void);
public:
QTextEdit *consoleBox;
StdRedirector<> *stdRedirector;
string bufferString;
};
#endif
The StdRedirector class is based on code from this forum post: http://www.qtforum.org/article/24554/displaying-std-cout-in-a-text-box.html
Take a look at the popen() function, it might do what you need.
Then you could pass the FILE * to a QTextStream and work in Qt style with it.
I suggest, rather than showing stdout in GUI, having own console output, which essentially means all messages you want to show to users you are sending to your own output.
This way you can have debug messages and such still available from console, wtih potential errors with connections and whatever that can happen and have fully controlled console output in GUI application. Of course this output can also be outputted to stdout so it is visible in console, but it also allows you to append a prefixs like WARNING LOG NOTICE NO_THIS_WENT_WRONG or whatever you want to show to users as your console entry.