Create a plugins

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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{}
}@

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You better append your second .pro file too.

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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.

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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...

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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.

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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

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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

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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
@

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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...

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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?

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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

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

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

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I just wanted to point out that if you compile your application in debug mode you should compile your plugins in debug mode too (same goes for release builds).

However - have you tried to "trace the module import":http://developer.qt.nokia.com/doc/qt-4.7/qdeclarativedebugging.html?

EDIT: Are you sure that path in your qmldir file is correct? You instruct qmake to place your library in a "lib" directory but your path points to the "debug" directory. -As far as I have understood the documentation you do not need both - the qmldir and the import statement. You can omit one.-

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yes, i give the path to the location of NGWidgets.dll , and this dll is locate in the debug dir of the plugin project and also in the lib directory (in 2 cases it's not recognize the "module")...

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The .dll in your debug directory is most likely an outdated version, as all new versions are moved to the lib directory (as specified as DESTDIR in the .pro file). You are pointing to the wrong directory in your qmldir file.

Have you already tried tracing the module import?

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ok - you right , i changed it to :
@plugin NGWidgets C:/Qt/Projects/NGWidgets-build-desktop/lib@
but still have the same problem

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Have you already tried tracing the module import?

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this is the output:
QDeclarativeImportDatabase::addImportPath: "C:\QtSDK\Desktop\Qt\4.7.3\mingw\imports"
QDeclarativeImportDatabase::addImportPath: "C:/Qt/Projects/App-build-desktop/debug"
QDeclarativeImports(C:/Qt/Projects/App/app.qml)::addImport: "." -1.-1 File as ""
QDeclarativeImports(C:/Qt/Projects/App/app.qml)::addImport: "QtQuick" 1.0 Library as ""
QDeclarativeImports(C:/Qt/Projects/App/app.qml)::addImport: "NGWidgets" 1.0 Library as ""
C:/Qt/Projects/App/app.qml:3:1: module "NGWidgets" is not installed

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is this a good output?