std::is_base_of

Defined in header `<type_traits>`
template< class Base, class Derived > struct is_base_of;		(since C++11)

If Derived is derived from Base or if both are the same non-union class, provides the member constant value equal to true. Otherwise value is false.

Requires that Derived is a complete type if it is not the same type as Base and if both Base and Derived are class types.

Inherited from std::integral_constant

Member constants

value

[static]

true if Derived is derived from Base , 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>

[edit] Notes

Although no class is its own base, std::is_base_of<T, T>::value is true because the intent of the trait is to model the "is-a" relationship, and T is a T. Despite that, std::is_base_of<int, int>::value is false because only classes participate in the relationship that this trait models.

[edit] Example

Run this code

#include <iostream>
#include <type_traits>
 
class A {};
 
class B : A {};
 
class C {};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << "a2b: " << std::is_base_of<A, B>::value << '\n';
    std::cout << "b2a: " << std::is_base_of<B, A>::value << '\n';
    std::cout << "c2b: " << std::is_base_of<C, B>::value << '\n';
    std::cout << "same type: " << std::is_base_of<C, C>::value << '\n';
}

Output:

a2b: true
b2a: false
c2b: false
same type: true

[edit] See also

std::experimental::is_base_of_v

(library fundamentals TS)

variable template alias of std::is_base_of::value
(variable template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
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Numerics library
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Regular expressions library (C++11)
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Technical Specifications

Type support (basic types, RTTI, type traits)
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bitset
hash (C++11)
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rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
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integer_sequence (C++14)
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swap
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forward (C++11)
move (C++11)
move_if_noexcept (C++11)
declval (C++11)