Thread: Function Template

How to declare function template inside class?

Code:

class CTime  
{
public:
	CTime(int mn, int hr);

	template<typename Any>
	  void max(Any no);
}; 

In the cpp file I am implementing max.

When I create instance in main and try calling max:


int main()
{
	CTime T(1,2);

	T.max(3);

	return 0;

}

I get a linking error for max.

Here is my .h file:

Code:

class CTime  
{
public:
	CTime(int mn, int hr);
	~CTime();
	
	template<typename Any>
		void max(Any no);
};

This is cpp file:

Code:

#include "Time.h"


CTime::CTime(int mn, int hr)
{

}

CTime::~CTime()
{

}


template<typename Any>
void CTime::max(Any no)
{
}

and this is main:

Code:

#include "Time.h"

int main()
{
	CTime T(1,2);

	T.max(3.8);

	return 0;

}

implementing in header ... makes the code look bad.. n does that mean that template function becomes inline?

oops!!

Now I get the following errors:

maincpp.obj : error LNK2001: unresolved external symbol "public: __thiscall CTime<int>::~CTime<int>(void)" (??1?$CTime@H@@QAE@XZ)
maincpp.obj : error LNK2001: unresolved external symbol "public: void __thiscall CTime<int>::max(int)" (?max@?$CTime@H@@QAEXH@Z)
maincpp.obj : error LNK2001: unresolved external symbol "public: __thiscall CTime<int>::CTime<int>(int,int)" (??0?$CTime@H@@QAE@HH@Z)

Hey Sly..

i don't think i missed anything.. btw, did u try compiling the code at ur end? did it work?

Yes, declaring in header makes it work.. but does that make the function inline?

sorry implementing in header makes it work ...but does that make the function inline?

No. If you put the implementation into the class definition, that will be the same as marking it as an inline function. But if you just move what you had in the source file to the bottom of the header file, it will not be marked for inlining.

Another option is to leave the implementation in the source file and #include the source file at the bottom of the header. This would only be a good idea if the source file only contained definitions for templated classes and functions.

Are you suggesting something like this?


.h file:

Code:

class CTime  
{
public:
	CTime(int mn, int hr);
	~CTime();
	
	template<typename Any>
		void max(Any no);
};

template<typename Any>
void CTime::max(Any no)
{
}

This is cpp file:

Code:

#include "Time.h"


CTime::CTime(int mn, int hr)
{

}

CTime::~CTime()
{

}

and this is main:

Code:

#include "Time.h"

int main()
{
	CTime T(1,2);

	T.max(3.8);

	return 0;

}

I need to modify the way I call max, cause it gives me error saying:
Failed to specialize function template 'void __thiscall CTime::max(Any)'
With the following template arguments:
'int'

How do I call the template function?