Create a plugins

ZapB

This "article":http://developer.qt.nokia.com/doc/qt-4.7/qml-extending-tutorial-index.html explains how to extend QML using C++ and in particular section 6 shows you how to make your custom QDeclarative items into a reusable plugin.

goli

in the second project- when i want to use the objects from the first project in qml file , i got this error: module "Operands" is not installed - for the line : import Operands 1.0
i created an object OperandItem in the 1st project, and write :
qmlRegisterType<OperandItem> ("Operands", 1, 0, "MYOperand");

and i am trying to use this from the qml in the 2nd project... in the qml the MYOperand is known, but i got this error .

ZapB

Did you follow the steps in the docs? ie have you actually made a plugin (a shared lib that can be loaded by your 2nd project)?

goli

in the 1st project i write :

@
#if defined(MY_NGWIDGETS_LIBRARY)

define MYSHARED_EXPORT Q_DECL_EXPORT

#else

define MYSHARED_EXPORT Q_DECL_IMPORT

#endif

class MYSHARED_EXPORT MyClass{...}
@

for each class that i want to use in the 2nd project.

2.in the pro file (of the 1st project) i write:
@
TARGET = NGWidgets
TEMPLATE = app
DEFINES += MY_NGWIDGETS_LIBRARY
CONFIG += qt plugin
DESTDIR = app
OBJECTS_DIR = tmp
MOC_DIR = tmp
@

i also create a qmldir file and write:

@
plugin NGWidgets-plugins app
@

then i tried to use the plugin from the 2nd project.
but it still say that the modules are not installed

Edit: Please use @ tags to delimit blocks of code etc.

ZapB

Well for a start the 1st project needs to have
@
TEMPLATE = lib
@
rather than "app" since you are trying to make a plugin which is a shared library.

goli

now i got this error:
The process could not be started: The system cannot find the file specified. - for the line:
@DESTDIR = lib

ZapB

What process? Can you post your 2 projects please? Either that or be alot more descriptive in what you are doing. You are not giving us enough information to understand what the problem is.

You will not be able to execute your 1st project since that will just be a plugin library not an application.

goli

1st project:

operanditem.h

@ #if defined(MY_NGWIDGETS_LIBRARY)

define MYSHARED_EXPORT Q_DECL_EXPORT

#else

define MYSHARED_EXPORT Q_DECL_IMPORT

#endif

class MYSHARED_EXPORT OperandItem : public QObject
{.....}@

main.c

@qmlRegisterType<OperandItem> (“Operands”, 1, 0, “MYOperand”);@

pro file

@QT += core gui
QT += declarative
QT += network
QT += xml

TARGET = NGWidgets
TEMPLATE = lib
DEFINES += MY_NGWIDGETS_LIBRARY
CONFIG += qt plugin
DESTDIR = lib
OBJECTS_DIR = tmp
MOC_DIR = tmp

SOURCES +=
main.cpp \
Operands/operanditem.cpp
HEADERS +=
Operands/operanditem.h

@

2nd project:

in some qml file i write:

@ import QtQuick 1.0
import Operands 1.0

Rectangle{
MYOperand{}
}@

lgeyer

You better append your second .pro file too.

ZapB

Please have another read through this "article":http://developer.qt.nokia.com/doc/qt-4.7/declarative-tutorials-extending-chapter6-plugins.html#id-8c522ec4-43c2-4344-a4a4-148efcc18b7d and you'll see that you also need to write a plugin class derived from QDeclarativeExtensionPlugin that your 2nd project's QML engine will call the registerTypes() function of in order to register them with your 2nd project.

This plugin class seems to be completely missing from you 1st project.

goli

i have this class inherit from QDeclarativeExtensionPlugin and create the plugin.
i don't know what i need to add to the 2nd project (in the pro file) to make it work with the new module...

ZapB

You need to edit the qmldir file in your 2nd project so that it points at the path where the plugin library from your 1st project is located.

goli

the dll file was created in the build-desktop directory(in the debug) and not in the QtCreator\lib\ directory... even when i copy the dll to this place it does not work

goli

in the pro file i write:

@QTPLUGIN += NGWidgets
LIBS += -L"C:/Qt/Projects/NGWidgets-build-desktop/debug"
LIBS += -lNGWidgets@

in the folder "C:/Qt/Projects/NGWidgets-build-desktop/debug"
i have the dll (NGWidgets.dll)

but i got the error:
:-1: error: cannot find -lngwidgetsd
collect2: ld returned 1 exit status

ZapB

I don't think that your 2nd project's .pro file needs to mention the NGWidgets plugin lib at all. The qmldir file tells the QDeclarativeEngine where it can dllopen your plugin library from.

Also the error message you posted does not match the .pro file you have posted the error message is referring to ngwidgetsd.dll whereas the .pro file mentions NGWidgets.dll (not the trailing d).

In your 1st project (the plugin one) make sure you are using the Q_EXPORT_PLUGIN2 macro as is mentioned in the docs:

@
Q_EXPORT_PLUGIN2( NGWidgets, NGWidgetsPlugin )
@

where I have assumed that your plugin class (the one derived from QDeclarativeExtensionPlugin) is called NGWidgetsPlugin (since you have not shown it to us).

Try using a qmldir file for your 2d project that looks like this:

@
plugin NGWidgets C:/Qt/Projects/NGWidgets-build-desktop/debug
@

and in your .qml file using

@
import NGWidgets 1.0
@

goli

that exaclly what i did - and i create alse qmldir file in the first project (as shown in the example)....

in this link : http://doc.qt.nokia.com/latest/plugins-howto.html
they say that the pro file of the 2nd project should be changed...

ZapB

I do not see anything in that document relating to qml plugins. Rather than this constant back and forth can you provide a zip file of your two projects that we can try to fix up for you please?

goli

i can't post all my code. but this is the main classes:

1st project :

ngwidgetsplugin.h

@#include <QDeclarativeExtensionPlugin>

class NGWidgetsPlugin: public QDeclarativeExtensionPlugin
{
Q_OBJECT
public:
void registerTypes(const char *uri);
};@

ngwidgetsplugin.cpp

@#include <QtDeclarative>
#include <QtPlugin>
//.....more includes for files

void NGWidgetsPlugin::registerTypes(const char *uri)
{
qmlRegisterType<OperandItem> (uri, 1, 0, "MYOperand");

   //.................

}

Q_EXPORT_PLUGIN2(NGWidgets, NGWidgetsPlugin)@

.pro

@QT += core gui
QT += declarative
QT += network

#TARGET = NGWidgets
TEMPLATE = lib
CONFIG += qt plugin
DESTDIR = lib
OBJECTS_DIR = tmp
MOC_DIR = tmp

SOURCES += ...
HEADERS += ...
OTHER_FILES += ...
@

qmldir

@plugin NGWidgets lib@

2nd project - use the plugin

.pro

@QT += core gui
QT += declarative
QT += network

SOURCES += ...
HEADERS += ...
OTHER_FILES += ...@

qmldir

@plugin NGWidgets C:/Qt/Projects/NGWidgets-build-desktop/debug @

app.qml

@import QtQuick 1.0
import NGWidgets 1.0

Rectangle
{
MYOperand{...}
}

@

i got the error : module "NGWidgets" is not installed
for line 2

lgeyer

Be also aware that you usually cannot mix release and debug code.

goli

so how can i connect to the plugin, that locate in the debug dir?