Need help on template

[Anuja]

Hi,


I have a template question

Header
template <class T>
class BaseClass {
public:
void isValid(T aId);
};

Cpp file
template <class T>
class BaseClass {
BaseClass::isValid(T aId) {
cout << aId << endl;
}
}


Derived class header
class DerivedClass: public BaseClass<short> {
};

It gives compile-time error saying undefined symbol
BaseClass<short>::isValid(short)

Isnt isValid method inherited ?

Thanks
Jay

 

[Ian Collins]

Hi,


I have a template question

Header
template <class T>
class BaseClass {
public:
void isValid(T aId);
};

Cpp file
template <class T>
class BaseClass {
BaseClass::isValid(T aId) {
cout << aId << endl;
}
}


Derived class header
class DerivedClass: public BaseClass<short> {
};

It gives compile-time error saying undefined symbol
BaseClass<short>::isValid(short)

Isnt isValid method inherited ?

Your compiler probably requires the method definition to be included in
the header.

 

[benben]

Hi,


I have a template question

Header
template <class T>
class BaseClass {
public:
void isValid(T aId);
};

Cpp file
template <class T>
class BaseClass {
BaseClass::isValid(T aId) {
cout << aId << endl;
}
}

Put whatever in the Cpp file back to the header. Read the FAQ and other
related posts to find out why.

Derived class header
class DerivedClass: public BaseClass<short> {
};

It gives compile-time error saying undefined symbol
BaseClass<short>::isValid(short)

Isnt isValid method inherited ?

It should have been link-time error? Are you positive that it is indeed
a compile time error?

Thanks
Jay

Regards,
Ben

P.S. I am just curious if you guys are all from the same
class/college/school. It has been a lot of post on the same topic since
the last three days.

 

[benben]

Oops, my previous reply seems like a premature judgment. Please ignore
it. Sorry.

With what you posted I can't pinpoint the exact error. Perhaps post more
code would help.

regards,
Ben

 

[ak]

The template class definition is not right. It'd go like:


template <class T>
void BaseClass<T>::isValid(T aId) {
std::cout << aId << std::endl;
};


Besides, make sure this template class definition is visible to the c++
compiler whenever a DerivedClass is declared.

And use g++ instead of gcc. (If you are using gnu)

Cheers,
AK

 

[ak]

I guess to make myself clearer, I better post the way I think it could
be done. Of course there is always more than one way to do it:

template <class T>
class BaseClass {
public:
void isValid(T aId);
};
#include <iostream>
#include <string>

#include "bc.hpp"

template <class T>
void BaseClass<T>::isValid(T aId) {
std::cout << aId << std::endl;
};
#include "bc.tpl"

#include "dc.hpp"

int main(int, char**) {

DerivedClass a;
a.isValid(1);

}

Hope these helps.

Cheers,
AK