LNK2019從模板派生時出錯

Question

我想實現派生自模板的PointArray類。這裏是什麼PointArray我的HPP文件的樣子：

#ifndef POINTARRAY_H 
#define POINTARRAY_H 
#include <iostream> 
#include <sstream> 
#include <stdio.h> 
#include "Array.hpp" 

using namespace Abhishek::CAD; 
using namespace Abhishek::CONTAINERS; 

namespace Abhishek 
{ 
    namespace CONTAINERS 
    { 
     class PointArray : public Array<Point> 
     { 
     public: 
      PointArray();//Default constrcutor. 
      PointArray(int size);//Constructor with size argument. 
      PointArray(const PointArray& arr);//Copy constructor. 
      ~PointArray();//Destructor. 
      double Length() const;//Length function. 
     }; 

    } 
} 


#endif 

我CPP是這樣的：

#include <iostream> 
#include <sstream> 
#include <stdio.h> 
#include "PointArray.hpp" 

using namespace Abhishek::CAD; 
using namespace Abhishek::CONTAINERS; 

namespace Abhishek 
{ 
    namespace CONTAINERS 
    { 
     //Default constructor. 
     PointArray::PointArray(): Array<Point>() 
     { 
      cout<<"Point arr default cons"<<endl; 
     } 

     //Constructor with size argument. 
     PointArray::PointArray(int size) : Array<Point>(size) 
     { 

     } 

     //Copy constructor. 
     PointArray::PointArray(const PointArray& arr) : Array<Point>(arr) 
     { 

     } 

     //destrcutor. 
     PointArray::~PointArray() 
     { 

     } 
    } 
} 

我得到的LNK錯誤：

 error LNK2019: unresolved external symbol "public: __thiscall Abhishek::CONTAINERS::Array<class Abhishek::CAD::Point>::Array<class Abhishek::CAD::Point>(void)" (??0?$Array@VPoint@CAD@Abhishek@@@CONTAINERS@Abhishek@@QAE@XZ) referenced in function "public: __thiscall Abhishek::CONTAINERS::PointArray::PointArray(void)" (??0PointArray@CONTAINERS@Abhishek@@QAE@XZ) 
1>PointArray.obj : error LNK2019: unresolved external symbol "public: __thiscall Abhishek::CONTAINERS::Array<class Abhishek::CAD::Point>::Array<class Abhishek::CAD::Point>(int)" (??0?$Array@VPoint@CAD@Abhishek@@@CONTAINERS@Abhishek@@QAE@H@Z) referenced in function "public: __thiscall Abhishek::CONTAINERS::PointArray::PointArray(int)" (??0PointArray@CONTAINERS@Abhishek@@QAE@H@Z) 
1>PointArray.obj : error LNK2019: unresolved external symbol "public: __thiscall Abhishek::CONTAINERS::Array<class Abhishek::CAD::Point>::Array<class Abhishek::CAD::Point>(class Abhishek::CONTAINERS::Array<class Abhishek::CAD::Point> const &)" (??0?$Array@VPoint@CAD@Abhishek@@@CONTAINERS@Abhishek@@QAE@ABV012@@Z) referenced in function "public: __thiscall Abhishek::CONTAINERS::PointArray::PointArray(class Abhishek::CONTAINERS::PointArray const &)" (??0PointArray@CONTAINERS@Abhishek@@QAE@ABV012@@Z) 
1>PointArray.obj : error LNK2019: unresolved external symbol "public: __thiscall Abhishek::CONTAINERS::Array<class Abhishek::CAD::Point>::~Array<class Abhishek::CAD::Point>(void)" (??1?$Array@VPoint@CAD@Abhishek@@@CONTAINERS@Abhishek@@QAE@XZ) referenced in function __unwindfunclet$??0PointArray@CONTAINERS@Abhishek@@QAE@XZ$0 
1>C:\Users\Rambo\Documents\Level 6\Section 4.2b\Exercise 3\Debug\Exercise 3.exe : fatal error LNK1120: 4 unresolved externals 

我不明白爲什麼這會正在發生。我包含了所有相關的頭文件和CPP文件。如果任何人都可以幫助，我會非常感激。

Answer 1

您忘了發佈最相關的標題：聲明導致錯誤的類模板的標題。幾乎可以肯定，那標題聲明Array模板的默認構造函數：

Array(); 

但沒有定義它;要麼沒有定義，要麼你在源文件中有一個定義。

無論哪種情況，您都會遇到錯誤，因爲模板必須在使用它們的任何翻譯單元中定義。這意味着您需要在標題中定義構造函數（和任何其他成員函數），以將它們包含在使用的地方。

如果這不是問題，那麼請張貼標題，以便我們可以進一步調查。