Static Virtual functions in c++
I have a base class and a derived one and 开发者_运维问答I want to change base functions while keeping them static as they should be passed to other functions as static.
How can I do that?
The ATL framework gets around the limitation of no virtual statics by making the base class be a template, and then having derived classes pass their class type as a template parameter. The base class can then call derived class statics when needed, eg:
template< class DerivedType >
class Base
{
public:
static void DoSomething() { DerivedType::DoSomethingElse(); }
};
class Derived1 : public Base<Derived1>
{
public:
static void DoSomethingElse() { ... }
};
class Derived2 : public Base<Derived2>
{
public:
static void DoSomethingElse() { ... }
};
This is known as Curiously recurring template pattern, which can be used to implement static polymorphism.
Do you mean you need a pointer to a static function (e.g. to pass as an argument to another function that requires a pointer to a static function), but you need to access that function pointer virtually? In that case, use a virtual function to get the function pointer:
typedef void (*function)();
void do_stuff_with_function(function);
struct Base {
virtual ~Base() {}
virtual function get_function() = 0;
};
struct Derived : Base {
function get_function() {return my_function;}
static void my_function();
};
Derived d;
do_stuff_with_function(d.get_function());
static function can not be virtual since they do not have an instance through which they are accessed. I do believe you can overwrite them though.
You can't have static virtual functions in C++.
Virtual functions typically rely on this
pointer to determine the type of function to be called at run time.
A static member function does not pass a this
so static virtual functions are not allowed in C++.
If i am correct in understanding ur question, then u can follow the following approach otherwise ignore..
have static function pointer in the base class.
in base class have a static function ( in which u call the function by using that static function pointer)..
in derived classes set that static function poiter to the function defination u wish to execute.. ( in base class u can set the function pointer to some default function).
You cannot have static virtual functions, because it doesn't make sense to have them.
精彩评论