[SOLVED] I can not create plugin.

CKurdu

I sampled from "echoplugin":http://qt-project.org/doc/qt-4.8/tools-echoplugin.html example to make own plugin.
My plugin Interface
@
#ifndef MODULEINTERFACE_H
#define MODULEINTERFACE_H
#include <QString>

class ModuleInterface
{
public:

virtual ~ModuleInterface() {}
virtual QString display(QString *);
virtual QString execute(QString *);
};

QT_BEGIN_NAMESPACE

#define ModuleInterface_iid "proje.tc.ModuleInterface"

Q_DECLARE_INTERFACE(ModuleInterface,ModuleInterface_iid)

QT_END_NAMESPACE

#endif // MODULEINTERFACE_H

@

But always I got these errors.
@
/home/ckurdu/Documents/my_works/C++/qt/my_projects/qtcms-modules/menu/menu/moduleinterface.h:16: error: expected identifier before string constant
#define ModuleInterface_iid "proje.tc.ModuleInterface"

/home/ckurdu/Documents/my_works/C++/qt/my_projects/qtcms-modules/menu/menu/moduleinterface.h:16: error: expected ',' or '...' before string constant
#define ModuleInterface_iid "proje.tc.ModuleInterface"

/home/ckurdu/bin/Qt_5_4/5.4/gcc_64/include/QtCore/qobjectdefs_impl.h:49: error: expected constructor, destructor, or type conversion before 'namespace'
namespace QtPrivate {
^
^ ^

@

My pro file

@
TEMPLATE = lib
CONFIG += plugin
QT += sql script
QT -= gui
SOURCES += menu.cpp
HEADERS += menu.h
moduleinterface.h
TARGET = $$qtLibraryTarget(qtcmsmenu)
#DESTDIR = ../plugins
#! [0]

EXAMPLE_FILES = menuplugin.json

DESTDIR = /home/ckurdu/Documents/my_works/C++/qt/qtbin/qtcms_modules/menu/

@

And I can't see any generated moc files.

What is the problem?

SGaist

Hi,

You need to either make display and execute pure virtual or give them an implementation.

On a side note, why are you passing pointers to QString ? Most of the time it's not needed. QString is one of the implicitly shared class of Qt.

CKurdu

Actually I have given them an implementation that I didn't write here. I solved the problem with changing the order of header files in real plugin file.
Firstly I included QObject and QtPlugin and after interface header file and problem disappear.

I will change the pointers. Thank you SGaist.

@
#ifndef MODULEPLUGIN_H
#define MODULEPLUGIN_H
#include <QObject>
#include <QtPlugin>
#include "moduleinterface.h" // I changed location for this line.

class ModulePlugin : public QObject, ModuleInterface
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "proje.tc.ModuleInterface")
Q_INTERFACES(ModuleInterface)
public:
QString display(QString *command) Q_DECL_OVERRIDE;
QString execute(QString *command) Q_DECL_OVERRIDE;
};

#endif // MODULEPLUGIN_H
@

moijhd

Q_DECLARE_INTERFACE is defined in qobject.h included through #include <QObject> which implies that you have to write #include <QObject> before #include "moduleinterface.h" (so that Q_DECLARE_INTERFACE is defined when parsing "moduleinterface.h") in the plugin.

I would recommend including <QObject> in the interface "moduleinterface.h" to avoid arguing in the order of the includes.

Yeah, it's an old post (a referenced one), but I played again with the plugins and I struggled a little...

Below, code compliant from Qt 4.1 (I guess) to Qt 5.8 (at least)

#ifndef PLUGININTERFACE_H
#define PLUGININTERFACE_H

#include <QString>

/** declare Q_DECLARE_INTERFACE */
#include <QObject>

#define PluginInterface_iid "PluginInterface"

class PluginInterface
{
public:
    virtual QString name() const = 0;
    virtual ~PluginInterface(){}
};

Q_DECLARE_INTERFACE(PluginInterface, PluginInterface_iid)

#endif // PLUGININTERFACE_H

#ifndef P1_H
#define P1_H

#include "p1_global.h"

#include "../pluginmanager/plugininterface.h"

class P1SHARED_EXPORT P1 : public QObject, public PluginInterface
{
    Q_OBJECT
#if QT_VERSION >= 0x050000
    Q_PLUGIN_METADATA(IID PluginInterface_iid".P1")
#endif
    Q_INTERFACES(PluginInterface)

public:
    virtual QString name() const;
};

#endif // P1_H

#ifndef P1_GLOBAL_H
#define P1_GLOBAL_H

#include <QtCore/qglobal.h>

#if defined(P1_LIBRARY)
#  define P1SHARED_EXPORT Q_DECL_EXPORT
#else
#  define P1SHARED_EXPORT Q_DECL_IMPORT
#endif

#endif // P1_GLOBAL_H

#include "p1.h"

#if 0x040100 <= QT_VERSION && QT_VERSION < 0x050000
#include <QtCore/qplugin.h>
#endif

QString P1::name() const
{
    return QString("P1");
}

#if 0x040100 <= QT_VERSION && QT_VERSION < 0x050000
Q_EXPORT_PLUGIN2(p1, P1)
#endif

#-------------------------------------------------
#
# Project created by QtCreator 2018-03-17T08:40:29
#
#-------------------------------------------------

QT       -= gui
CONFIG         += plugin
TARGET = p1
TEMPLATE = lib

DEFINES += P1_LIBRARY

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += p1.cpp

HEADERS += p1.h\
        p1_global.h