Long story short: I need to find the type of a variable to use it in the #if condition
macro. My typeof()
in the provided sample is an imagined function, expression, code I would like to know. If even exists...
Otherwise, is there any workaround?
Sample code:
template <class T>
class MyClass
{
T variable;
public:
#if typeof(T) == typeof(int)
// compile section A
#elif typeof(T) == typeof(string)
// compile section B
#endif
};
If you wish to provide some members and/or member functions on some condition, a way is inherit from implement classes via std::conditional_t
:
struct MyClassIntImpl {
void foo() {}
};
struct MyClassStringImpl {
void bar() {}
};
struct MyClassDefaultImpl {};
template <class T>
class MyClass : public
std::conditional_t<std::is_same_v<T, int>, MyClassIntImpl,
std::conditional_t<std::is_same_v<T, std::string>, MyClassStringImpl,
MyClassDefaultImpl>>
{
// ...
Where MyClassDefaultImpl
is simply the default case, as needed for std::conditional_t
.
Therefore a MyClass<int>
object will have the foo()
member function:
int main() {
MyClass<int> u;
u.foo();
}
This has some benefits over specialization:
std::is_integral_v
, which you can't easily do with specializations.
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