Template Question

[gareth19]

why doesnt this work?

// global
struct s
{
   float x;
   float y;
};

// set.h
Class CSet
{
std::vector<s> mStructData;
std::vector<int> m_intData;

template<typename T>
void inline	 setdata(	std::vector<T>& TData )
{
	if ( m_bool == TRUE )
	   m_StructData.assign( TData.begin(), TData.end() );
	else 
	   m_intData.assign( TData.begin(), TData.end() );
};

};

/***********************************************/

//try.h
CSet	m_Set;
// try.cpp
std::vector<s> sData;
std::vector<int> intData;
if ( m_bool )
   m_Set.setdata( sData );
else
   m_Set.setdata( intData );

I get error C2664 ... Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
... C\...\try.cpp(178) : see reference to function template instantiation ...

Thx.

[Assmaster]

What's this m_bool variable? You've used it twice, but havent defined it anywhere.

And why does setdata need to be templated? If it's only to save you the trouble of writing one setdata for each of the member vectors, it's not worth it. It'll only clutter up your code and make it harder to read for other programmers (and yourself 4 months from now). Make one setdata for each of the member vectors.

We'll need to see some real compilable code to be able to answer your question further. This code doesn't make sense to me...

[Assmaster]

Originally posted by me
And why does setdata need to be templated? If it's only to save you the trouble of writing one setdata for each of the member vectors, it's not worth it. It'll only clutter up your code and make it harder to read for other programmers (and yourself 4 months from now). Make one setdata for each of the member vectors.

In fact... This won't work at all, and that's probably the error you're recieving.

When the compiler sees a templated function like yours, and you instantiate it for one type, it will compile the entire function with the template parameter you pass to it, and in your case that will lead to either one or the other assign line to not compile. (Wether or not the assign functions will actually be called, doesn't matter!)

If you pass a std::vector<int> to your func, the m_StructData.assign will not compile since it's assigning a std::vector<int> to a std::vector<s>. If you pass a std::vector<s>, it's the other way around. Any other type, and neither will compile.

[Graham]

I agree with Assmaster: overload the function - don't bother with templates.


One other point in addition to Assmaster's correct reply: "void inline" should be "inline void".