Linker error for a template method

Question

I'm having problems with the linker.

It gives me the following error:

[Linker error] undefined reference to `bool Polis :: deleteEdifice <Mine> (int) '

The prototype is declared as follows:

template <typename T> bool deleteEdifice(int);

deleteEdifice is empty, that does not do anything for now but it does not work.

The call to the prototype is:

obj->deleteEdifice<Mine>(3);

I also tried to do:

obj->template deleteEdifice<Mine>(3);

Print the following error:

`template' (as a disambiguator) is only allowed within templates

Could you tell me what am I doing wrong.

Answer 1

This

template <typename T> bool deleteEdifice(int);

does not mean it is empty, it means it is undefined like the error [Linker error] undefined reference

This

template <typename T> bool deleteEdifice(int) { return false; }

is empty

Answer 2

I'm having problems with the linker. It gives me the following error: [Linker error] undefined reference to `bool Polis :: deleteEdifice (int) '

I'm assuming your code looks like this:

//.h file
class Polis
{
  public:
    //...constructor etc...
    template <class T>
    bool deleteEdifice( int );
};

Also .h file

//, where definition of template is visible at 
// point of instantiation - remember, template is instantiated
// when used (in compilation unit where used), therefore its 
// definition has to be visible in the scope where used. It is
// only instantiated when used... If it's definition is not 
// available at the point of instantiation (where called for 
// a function template), it is never 
// compiled.

template <class T>
bool Polis::deleteEdifice( int )
{
  //Implementation here...
}