The relationship between a class template and an individual class is like the relationship between a class and an individual object. An individual class defines how a group of objects can be constructed, while a class template defines how a group of classes can be generated.
Note the distinction between the terms class template and template class:
A template definition is identical to any valid class definition that the template might generate, except for the following:
template< template-parameter-list >
where template-parameter-list is a comma-separated list
of one or more of the following kinds of template parameters:
A class template can be declared without being defined by using an elaborated type specifier. For example:
template<class L, class T> class Key;
This reserves the name as a class template name. All template declarations for a class template must have the same types and number of template arguments. Only one template declaration containing the class definition is allowed.
Objects and function members of individual template classes can be accessed by any of the techniques used to access ordinary class member objects and functions. Given a class template:
template<class T> class Vehicle
{
public:
Vehicle() { /* ... */ } // constructor
~Vehicle() {}; // destructor
T kind[16];
T* drive();
static void roadmap();
// ...
};
and the declaration:
Vehicle<char> bicycle; // instantiates the template
the constructor, the constructed object, and the member function drive() can be accessed with any of the following (assuming the standard header file string.h is included in the program file):
constructor |
|
object bicycle |
|
function drive() | char* n = bicycle.drive(); |
function roadmap() | Vehicle<char>::roadmap(); |
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