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cannot convert from pointer to base class 'QObject' to pointer to derived class 'subClass' via virtual base 'baseClass'

2019年06月05日  | 移动技术网IT编程  | 我要评论

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qt 编译不过的另一个问题：

1. 新建一个console工程

qt -= gui

config += c++11 console
config -= app_bundle

# the following define makes your compiler emit warnings if you use
# any feature of qt which as been marked 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 += \
        main.cpp \
    baseclass.cpp \
    subclass.cpp \
    subclass2.cpp
    #grandclass.cpp

# default rules for deployment.
qnx: target.path = /tmp/$${target}/bin
else: unix:!android: target.path = /opt/$${target}/bin
!isempty(target.path): installs += target

headers += \
    baseclass.h \
    subclass.h \
    subclass2.h
    #grandclass.h

2. 添加baseclass

baseclass.h

#ifndef baseclass_h
#define baseclass_h

#include "qobject"

class baseclass: public qobject
{
    q_object

public:
    baseclass(qobject * p = 0);
    virtual ~baseclass() {}

    virtual void vmethod(int) = 0;

signals:
    void signal1();


};

#endif // baseclass_h

baseclass.cpp

#include "baseclass.h"

baseclass::baseclass(qobject * p) : qobject(p)
{

}

3. 添加subclass

subclass.h

#ifndef subclass_h
#define subclass_h

#include "baseclass.h"

class subclass: virtual public baseclass
{
    q_object

public:
    subclass(qobject * p = 0);
    virtual ~subclass() {};
    virtual void vmethod(int) = 0;

signals:
    void signal2();

};

#endif // subclass_h

subclass.cpp

#include "subclass.h"

subclass::subclass(qobject * p) : baseclass (p)
{

}

4. 添加subclass2

subclass2.h

#ifndef subclass2_h
#define subclass2_h

#include "baseclass.h"

class subclass2 : virtual public baseclass
{
    q_object

public:
    subclass2(qobject * p = 0);

    virtual void vmethod(int) = 0;

};

#endif // subclass2_h

subclass2.cpp

#include "subclass2.h"

subclass2::subclass2(qobject * p) : baseclass (p)
{

}

5 main.cpp

#include <qcoreapplication>
#include "subclass.h"
//#include "grandclass.h"

int main(int argc, char *argv[])
{
    qcoreapplication a(argc, argv);


    //grandclass * sub = new grandclass();

    return a.exec();
}

 

编译报错：/build-testqtsignalbug-qt5_9_4_zynq-debug/moc_subclass.cpp:68: error: cannot convert from pointer to base class 'qobject' to pointer to derived class 'subclass' via virtual base 'baseclass'

subclass *_t = static_cast<subclass *>(_o);
^

 

 

解决方法： 将subclass里的signals 删掉， 即不在subclass里声明信号量。

原因：不详。

 

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