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Showing content from https://cplusplus.com/reference/type_traits/is_object/ below:

class template

<type_traits>

std::is_object

template <class T> struct is_object;

Is object type

Trait class that identifies whether T is an object type. An object type is a type with storage associated to it, which includes all types except functions, references and void.

It inherits from integral_constant as being either true_type or false_type, depending on whether T is an object type, no matter its const and/or volative qualification.

This is a compound type trait defined with the same behavior as:

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template<class T>
struct is_object : std::integral_constant < bool,
         !is_function<T>::value && !is_void<T>::value && !is_reference<T>::value> {};

Template parameters

T: A type.

Member types Inherited from integral_constant:

Member constants Inherited from integral_constant:
member constant definition value either true or false
Member functions Inherited from integral_constant:

operator bool: Returns value (public member function)

Example

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

class A {};

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_object:" << std::endl;
  std::cout << "int: " << std::is_object<int>::value << std::endl;
  std::cout << "A: " << std::is_object<A>::value << std::endl;
  std::cout << "A&: " << std::is_object<A&>::value << std::endl;
  std::cout << "A*: " << std::is_object<A*>::value << std::endl;
  std::cout << "int(int): " << std::is_object<int(int)>::value << std::endl;
  std::cout << "int(*)(int): " << std::is_object<int(*)(int)>::value << std::endl;
  return 0;
}

Output:

is_object:
int: true
A: true
A&: false
A*: true
int(int): false
int(*)(int): true