我在带有 GCC 的 Linux 上使用 Qt 4.8.3。我正在尝试使用 QtPlugin 创建模块化应用程序。该应用程序描述了一些基本功能，然后大量插件将提供所有独特的功能。每个插件使用一个工厂来提供一个类的多个实例，并由工厂类和要提供的类组成。
目前，应用程序正在编译，但没有执行，我收到了诸如Cannot load library ~: (~: undefined symbol: _ZTI8Base16staticMetaObjectE). 我不确定如何解决此错误。删除对 Base 的所有提及可以解决问题，但是实例需要从该类派生，所以我认为这不会起作用。
我在下面的项目结构中包含了可执行文件和一个插件（它们目前都是相同的并且有相同的问题）。
非常感谢你的协助。
目录结构
main_project
+- main_project.pro
+- app/
| +- app.pro
| +- main.cpp
| +- factoryinterface.h
| +- base.h
| +- base.cpp
|
+- counter/
+- counter.pro
+- counter.h
+- counterfactory.cpp
+- counterfactory.h
+- counter.cpp
main_project.pro
TEMPLATE = subdirs
SUBDIRS += \
app \
counter
应用程序.pro
QT += core
QT -= gui
DESTDIR = ../
TARGET = app_exec
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
base.cpp
HEADERS += \
base.h \
factoryinterface.h
工厂接口.h
#ifndef FACTORYINTERFACE_H
#define FACTORYINTERFACE_H
#include <QtPlugin>
#include "base.h"
class FactoryInterface {
public:
virtual ~FactoryInterface() {}
virtual Base *get() = 0;
virtual QString name() = 0;
};
Q_DECLARE_INTERFACE(FactoryInterface,
"com.example.FactoryInterface/1.0")
#endif // FACTORYINTERFACE_H
基础.h
#ifndef BASE_H
#define BASE_H
#include <QObject>
#include <QString>
#include <QStringList>
#include <QHash>
class Base : public QObject {
Q_OBJECT
public:
Base(QObject *parent = 0);
virtual ~Base();
virtual QString name();
signals:
public slots:
protected:
QString name_;
};
#endif // BASE_H
基础.cpp
#include "base.h"
Base::Base(QObject *parent) :
QObject(parent)
{
}
Base::~Base()
{
}
QString Base::name()
{
return name_;
}
主文件
#include <QtCore/QCoreApplication>
#include <QDir>
#include <QPluginLoader>
#include <QDebug>
#include "factoryinterface.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QDir pluginDir(a.applicationDirPath());
pluginDir.cd("plugins");
foreach(QString filename, pluginDir.entryList(QDir::Files))
{
QPluginLoader loader(pluginDir.absoluteFilePath(filename));
QObject *plugin = loader.instance();
if (plugin)
{
FactoryInterface *i = qobject_cast<FactoryInterface*>(plugin);
if (i)
{
qDebug() << " :" << i->name();
}
} else {
qDebug() << loader.errorString();
}
}
return a.exec();
}
计数器.pro
QT -= gui
CONFIG += plugin
TARGET = $$qtLibraryTarget(counter)
TEMPLATE = lib
DEFINES += COUNTER_LIBRARY
SOURCES += counter.cpp \
counterfactory.cpp
HEADERS += counter.h \
counterfactory.h
INCLUDEPATH += ../app
DESTDIR = ../plugins
symbian {
MMP_RULES += EXPORTUNFROZEN
TARGET.UID3 = 0xE5B38B75
TARGET.CAPABILITY =
TARGET.EPOCALLOWDLLDATA = 1
addFiles.sources = counter.dll
addFiles.path = !:/sys/bin
DEPLOYMENT += addFiles
}
unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}
计数器.h
#ifndef COUNTER_H
#define COUNTER_H
#include <QObject>
#include "base.h"
class Counter : public Base {
Q_OBJECT
public:
Counter();
};
#endif // COUNTER_H
计数器.cpp
#include "counter.h"
Counter::Counter()
{
name_ = "Counter";
}
反工厂.h
#ifndef COUNTER_H
#define COUNTER_H
#include <QObject>
#include "factoryinterface.h"
#include "base.h"
#include "counter.h"
class CounterFactory : public QObject, public FactoryInterface
{
Q_OBJECT
Q_INTERFACES(FactoryInterface)
public:
explicit CounterFactory(QObject *parent = 0);
Base *get();
QString name();
signals:
public slots:
};
#endif // COUNTER_H
反工厂.cpp
#include "counterfactory.h"
CounterFactory::CounterFactory(QObject *parent) :
QObject(parent)
{
}
Base *CounterFactory::get()
{
return new Counter;
}
QString CounterFactory::name()
{
return "Counter";
}
Q_EXPORT_PLUGIN2(counter, CounterFactory)
编辑：在调试模式下编译后更新错误消息。
编辑：我尝试导出/导入 BaseNode 类，但这也不起作用。我不确定这是完全不正确还是我做错了。对 Base 类进行了以下更改（将 BASE_LIBRARY 添加到 app.pro 文件中的 DEFINES 中）：
#include <QtCore/qglobal.h>
#if defined(BASE_LIBRARY)
# define BASESHARED_EXPORT Q_DECL_EXPORT
#else
# define BASESHARED_EXPORT Q_DECL_IMPORT
#endif
class BASESHARED_EXPORT Base : public QObject {