<type_traits>

類模板
<type_traits>

std::is_base_of

template <class Base, class Derived> struct is_base_of;
Is base class of

用於識別Baseis a base class of (or the same class as)Derived, without regard to theirconstand/orvolatilequalification. Only classes that are not unions are considered.

該類繼承自 integral_constant,根據Derivedinherits fromBase.


模板引數

Base
一個型別。
Derived
一個型別。
This shall be a complete type if bothBaseDerivedare different class types.
This shall be a complete type if bothBaseDerivedare different non-union class types.

成員型別

Inherited from integral_constant
成員型別定義
value_typebool
型別true_type 或 false_type

成員常量

Inherited from integral_constant
成員常量定義
trueorfalse

成員函式

Inherited from integral_constant

示例

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// is_base_of example
#include <iostream>
#include <type_traits>

struct A {};
struct B : A {};

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_base_of:" << std::endl;
  std::cout << "int, int: " << std::is_base_of<int,int>::value << std::endl;
  std::cout << "A, A: " << std::is_base_of<A,A>::value << std::endl;
  std::cout << "A, B: " << std::is_base_of<A,B>::value << std::endl;
  std::cout << "A, const B: " << std::is_base_of<A,const B>::value << std::endl;
  std::cout << "A&, B&: " << std::is_base_of<A&,B&>::value << std::endl;
  std::cout << "B, A: " << std::is_base_of<B,A>::value << std::endl;
  return 0;
}

輸出
is_base_of:
int, int: false
A, A: true
A, B: true
A, const B: true
A&, B&: false
B, A: false


另見