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std::is_abstract

STD：：是[医]摘要

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

如果T是抽象类%28，即声明或继承至少一个纯虚拟函数%29的非联合类提供了成员常量。value平等true.对于任何其他类型，value是false...

如果T是非工会类类型，T应该是一个完整的类型；否则，该行为是未定义的。

模板参数

T-a type to check

辅助变量模板

template< class T > inline constexpr bool is_abstract_v = is_abstract::value;​(since C++17)

继承自STD：积分[医]常量

成员常数

value statictrue if T is an abstract class type , false otherwise (public static member constant)

成员函数

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

成员类型

TypeDefinition
value_typebool
typestd::integral_constant<bool, value>

例

二次

#include <iostream>
#include <type_traits>
 
struct A {
    int m;
};
 
struct B {
    virtual void foo(
};
 
struct C {
    virtual void foo() = 0;
};
 
struct D : C {};
 
int main()
{
    std::cout << std::boolalpha;
    std::cout << std::is_abstract<A>::value << '\n';
    std::cout << std::is_abstract<B>::value << '\n';
    std::cout << std::is_abstract<C>::value << '\n';
    std::cout << std::is_abstract<D>::value << '\n';
}

二次

产出：

二次

false
false
true
true

二次

另见

is_class (C++11)checks if a type is a non-union class type (class template)
is_polymorphic (C++11)checks if a type is polymorphic class type (class template)

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http：//en.cppreference.com/w/cpp/type/is[医]摘要

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