std::is_member_pointer

 

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Defined in header <type_traits>
template< class T > struct is_member_pointer;		(since C++11)

std::is_member_pointer is a UnaryTypeTrait.

If T is pointer to non-static member object or a pointer to non-static member function, provides the member constant value equal true. For any other type, value is false.

If the program adds specializations for std::is_member_pointer or std::is_member_pointer_v, the behavior is undefined.

Template parameters

T

-

a type to check

Helper variable template

template< class T > constexpr bool is_member_pointer_v = is_member_pointer<T>::value;		(since C++17)

Inherited from std::integral_constant

Member constants

value [static]

true if T is a member pointer type, false otherwise (public static member constant)

Member functions

operator bool	converts the object to bool, returns value (public member function)
operator() (C++14)	returns value (public member function)

Member types

Type	Definition
value_type	bool
type	std::integral_constant<bool, value>

Possible implementation

template<class T> struct is_member_pointer_helper : std::false_type {};   template<class T, class U> struct is_member_pointer_helper<T U::*> : std::true_type {};   template<class T> struct is_member_pointer : is_member_pointer_helper<typename std::remove_cv<T>::type> {};

Example

Run this code

#include <cassert>
#include <type_traits>
 
static_assert(!std::is_member_pointer_v<int*>);
 
struct S
{
    int i{42};
    int foo() { return 0xF00; }
};
using mem_int_ptr_t = int S::*;
using mem_fun_ptr_t = int (S::*)();
static_assert(std::is_member_pointer_v<mem_int_ptr_t>);
static_assert(std::is_member_pointer_v<mem_fun_ptr_t>);
 
int main()
{
    S s;
 
    mem_int_ptr_t pm = &S::i;
    assert(s.i == s.*pm);
 
    mem_fun_ptr_t pmf = &S::foo;
    assert((s.*pmf)() == s.foo());
}

See also

is_pointer (C++11)	checks if a type is a pointer type (class template)
is_member_object_pointer (C++11)	checks if a type is a pointer to a non-static member object (class template)
is_member_function_pointer (C++11)	checks if a type is a pointer to a non-static member function (class template)