std::is_class

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

Checks whether T is an class or struct type. Provides the member constant value which is equal to true, if T is an class or struct type (but not union). Otherwise, value is equal to false.

Inherited from std::integral_constant

Member constants

value

[static]

true if T is a class or struct , false otherwise
(public static member constant)

Member functions

operator bool

converts the object to bool, returns value
(public member function)

Member types

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

[edit] Possible implementation

namespace detail {
    template <class T> char test(int T::*);
    struct two { char c[2]; };
    template <class T> two test(...);
}
 
template <class T>
struct is_class : std::integral_constant<bool, sizeof(detail::test<T>(0))==1
                                            && !std::is_union<T>::value> {};

[edit] Example

Run this code

#include <iostream>
#include <type_traits>
 
struct A {};
 
class B {};
 
enum class C {};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_class<A>::value << '\n';
    std::cout << std::is_class<B>::value << '\n';
    std::cout << std::is_class<C>::value << '\n';
    std::cout << std::is_class<int>::value << '\n';
}

Output:

true
true
false
false

[edit] See also

is_union

(C++11)

checks if a type is an union type
(class template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Pairs and tuples
pair
tuple (C++11)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
Swap, forward and move
swap
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
declval (C++11)