链接器错误“未解析的外部符号”：使用模板 [英] Linker error 'unresolved external symbol' : working with templates

问题描述

我有一个基于模板的类[Allotter.h& Allotter.cpp]：

  template< typename allotType> class Allotter {
 public：
 Allotter（）; 
 quint32 getAllotment（allotType *）; 
 bool removeAllotment（quint32，int auto_destruct = 0）; 
 
 private：
 QVector< QPair< quint32，allotType *>> indexReg; 
 int init_topIndex; 
}; 
  

，它的用法显示为[ActiveListener.h& ActiveListener.cpp]：

  class ActiveListener：public QObject {
 Q_OBJECT 
 
 public： 
 ActiveListener（）; 
 
私有插槽：
 void processConnections（）; 
 void readFromSocket（int）; 
 
 private：
 QTcpServer * rootServer; 
 QSignalMapper * signalGate; 
 Allotter< QTcpSocket> TcpAllotter; 
}; 
  

我没有显示完整的定义，因为它并不重要。问题是当我编译，所有文件编译正确。这些文件在一个VC ++项目中。早些时候，当我没有使用基于模板的方法 Allotter 时，一切都在编译和链接良好。但现在，我得到这个错误：

  1> ActiveListener.obj：error LNK2019：未解析的外部符号public：__thiscall Allotter<在函数public：__thiscall ActiveListener :: ActiveListener（void）中引用的类QTcpSocket> :: Allotter< class QTcpSocket>（void）（?? 0？$ Allotter @ VQTcpSocket @@@@ QAE @ XZ） @@ QAE @ XZ）
 1> ActiveListener.obj：error LNK2019：未解析的外部符号public：unsigned int __thiscall Allotter< class QTcpSocket> :: getAllotment（class QTcpSocket *）（？getAllotment @？$ Allotter @函数private：void __thiscall ActiveListener :: processConnections（void）（？processConnections @ ActiveListener @@ AAEXXZ）中引用的VQTcpSocket @@@@ QAEIPAVQTcpSocket @@@ Z 
   ActiveListener :: ActiveListener（）根本没有提供任何引用。p $ p> 
 
  Allotter< QTcpSocket> :: Allotter（）。然而第二个参考文献存在。但我不明白为什么链接器不能解析这个外部符号。
 
 
 
错误出现之前的构建输出是：
  1> Moc'ing ActiveListener.h ... 
 1>正在编译... 
 1> stdafx.cpp 
 1> Compiling ... 
 1> ActiveListener.cpp 
 1> Allotter.cpp 
 1> moc_ActiveListener.cpp 
 1> main.cpp 
 1>正在生成代码... 
 1>链接... 
  
任何这是相关的，主要是因为所有这些以前工作完美。这只是，我使用模板后，导致一个问题。 
任何帮助将不胜感激。非常感谢。
解决方案
您不能将模板分割为.h和.cpp文件 - 您需要将完整的代码.h文件中的模板。
 
I have a template based class [Allotter.h & Allotter.cpp]:
template <typename allotType> class Allotter {
public:
 Allotter();
 quint32 getAllotment(allotType*);
 bool removeAllotment(quint32, int auto_destruct = 0);

private:
 QVector<QPair<quint32, allotType*>> indexReg;
 int init_topIndex;
};
and it's usage is shown as [ActiveListener.h & ActiveListener.cpp]:
class ActiveListener: public QObject {
 Q_OBJECT

public:
 ActiveListener();

private slots:
    void processConnections();
    void readFromSocket(int);

private:
 QTcpServer* rootServer;
 QSignalMapper* signalGate;
 Allotter<QTcpSocket> TcpAllotter;
};
I am not showing the complete definitions, since it doesn't really matter. The problem is when I compile, all files compile properly. The files are in a VC++ project. Earlier when I did not use a template-based approach for Allotter, everything was compiling and linking fine. But now, I get this error:
1>ActiveListener.obj : error LNK2019: unresolved external symbol "public: __thiscall Allotter<class QTcpSocket>::Allotter<class QTcpSocket>(void)" (??0?$Allotter@VQTcpSocket@@@@QAE@XZ) referenced in function "public: __thiscall ActiveListener::ActiveListener(void)" (??0ActiveListener@@QAE@XZ)
1>ActiveListener.obj : error LNK2019: unresolved external symbol "public: unsigned int __thiscall Allotter<class QTcpSocket>::getAllotment(class QTcpSocket *)" (?getAllotment@?$Allotter@VQTcpSocket@@@@QAEIPAVQTcpSocket@@@Z) referenced in function "private: void __thiscall ActiveListener::processConnections(void)" (?processConnections@ActiveListener@@AAEXXZ)
The surprising thing is, that the constructor, ActiveListener::ActiveListener() does not make any reference at all Allotter<QTcpSocket>::Allotter(). The second reference however does exist. But I don't understand why the linker isn't able to resolve this external symbol.

The build output just before the errors appear is:
1>Moc'ing ActiveListener.h...
1>Compiling...
1>stdafx.cpp
1>Compiling...
1>ActiveListener.cpp
1>Allotter.cpp
1>moc_ActiveListener.cpp
1>main.cpp
1>Generating Code...
1>Linking...
I don't understand if any of this is relevant, mostly because all this used to work perfectly before. It's just that after I use templates a problem is caused.
Any help will be appreciated. Thanks a lot.
解决方案
You cannot split templates into .h and .cpp files - you need to put the complete code for the template in the .h file.

                        
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