When do we use Template classes

[rsodimbakam]

Hi,
Can anyone explain me when do we use Template classes ?

Thanks

[GNiewerth]

There are several cases where you can use template classes/methods :

- templates can be used for static polymorphism.
- templates can be used when an algorithm works on different types that meet certain criteria.
- templates can be used for meta programming to optimize algorithms at compile time instead of runtime (template meta programming)

[ltcmelo]

Since you're apparently starting with templates, you can primarily think of using templates whenever you need to construct a class or an algorithm that works for any kind of data type: primitive types like int and double and/or user-defined ones. (This is basically a generalization of GNiewerth's second item.)

Once you get over it you'll probably be interested on doing some fancy things. And then there's a whole new story that would relate to the other items mentioned by GNiewerth.

[Hannson]

I'm using templates for a "super" class in a object-oriented DBMS. (Sounds more complex than it is)

I can easily create different datatypes in the DBMS by creating a class that inherit the superclass like:

class stringProperty : property<string>
{
// some stringProperty methods etc..
}

So to sum it up, for me template classes are about code re-use. Why bother rewriting a class for another datatype when you can write "template<class T>" on top and replace the otherwise fixed datatypes with the T varable datatype. Then the class can be used for all datatypes/classes - pretty neat!

[Russco]

Its also worth noting that templates classes can be made using a non-type template parameter.

Heres an example from my latest project.

template < uint N >
class Sequence
{
private:
IntVec sequence_;
Sequence( const Sequence& ); 
Sequence& operator =( const Sequence& );
public:
Sequence()
{
sequence_.reserve( N );
for ( int i = 1; i <= N; ++i )
{
sequence_.push_back( i );
}
Shuffle();
}

const IntVec& GetSequence() const
{
return sequence_;
}
staticvoid Randomize( uint def = 0 )
{
if ( def == 0 )
def = static_cast<uint>( std::time( 0 ) );
std::srand( def );
}

void Shuffle()
{
std::random_shuffle( sequence_.begin(), sequence_.end() );
}
};

[Russco]

Hmmm seems msvc9 has awful cut/paste trouble. Gives fancy syntax colouring but cant preserve indentation grrr