Question

以下是运行良好的代码

class HttpService {
public:
    virtual ~HttpService(); // implemented in .cpp
protected:
    HttpService(struct MHD_Connection *conn) {}
};
class HttpFileService : public HttpService
{
public:
    virtual ~HttpFileService() ; // implemented in .cpp
protected:
    HttpFileService(struct MHD_Connection *conn) : HttpService(conn) {}
};

现在，当我HttpService QObject的派生类时，如下所示：

#include <QObject>                      // change #1
class HttpService  : public QObject {   // change #2
    Q_OBJECT                            // change #3
public:
    virtual ~HttpService();
protected:
    HttpService(struct MHD_Connection *conn) {}
};

class HttpFileService : public HttpService {
    Q_OBJECT                            // change #4
public:
    virtual ~HttpFileService() ;
protected:
    HttpFileService(struct MHD_Connection *conn) : HttpService(conn) {}
};

我遇到以下链接错误：

Undefined symbols for architecture x86_64:
  "vtable for HttpService", referenced from:
      HttpService::~HttpService()in httpservice.o

将HttpService的构造函数更改为以下内容对

无效

explicit HttpService(QObject *parent = 0) : QObject(parent)

Answer 1

强制运行qmake并查看它是否有效。

Answer 2

您是否链接到正确的qt库？

Answer 3

你在调用moc编译器吗？如果没有，删除Q_OBJECT宏！你是否包含/链接moc-compilation的结果？

具有虚函数的类，从QObject派生时，会导致链接错误

3 个答案: