Question

i created a template that contains a map.
when i try to create an instance of that template i encounter a linking problem with the constructor and destructor.
also, when i try to create an instance in main it skips the line while debugging, and doesn’t even show it in the locals list.
it doesn’t compile “DataBase db;” unless i add “()” after db. (that’s the way i try to initiate the instance in main).

the code:

h:

template <class keyVal,class searchVal, class T>  
class DataBase  
{  
private:  
    map<keyVal,pair<searchVal,T*>*> DB;  
public :  
    DataBase();  
    virtual ~DataBase();    
}; 

cpp:

#include "DataBase.h"  

template <class keyVal,class searchVal, class T>  
DataBase<keyVal,searchVal,T>::DataBase()  
{}  

template <class keyVal,class searchVal, class T>  
DataBase<keyVal,searchVal,T>::~DataBase()  
{}

thanks

Answer 1

Add the implementation of template classes (and functions) directly in the header file:

template <class keyVal,class searchVal, class T>  
class DataBase  
{  
private:  
    map<keyVal,pair<searchVal,T*>*> DB;
public :  
    DataBase() {};  
    virtual ~DataBase() {};    
};