std::any::has_value(3)

NAME
std::any::has_value - std::any::has_value

Synopsis
   bool has_value() const noexcept; (since C++17)
   Checks whether the object contains a value.

Parameters
   (none)

Return value
   true if instance contains a value, otherwise false.

Example
// Run this code
 #include <any>
 #include <iostream>
 #include <string>
 int main()
 {
     std::boolalpha(std::cout);
     std::any a0;
     std::cout << "a0.has_value(): " << a0.has_value() << '\n';
     std::any a1 = 42;
     std::cout << "a1.has_value(): " << a1.has_value() << '\n';
     std::cout << "a1 = " << std::any_cast<int>(a1) << '\n';
     a1.reset();
     std::cout << "a1.has_value(): " << a1.has_value() << '\n';
     auto a2 = std::make_any<std::string>("Milky Way");
     std::cout << "a2.has_value(): " << a2.has_value() << '\n';
     std::cout << "a2 = \"" << std::any_cast<std::string&>(a2) << "\"\n";
     a2.reset();
     std::cout << "a2.has_value(): " << a2.has_value() << '\n';
 }

Output:
 a0.has_value(): false
 a1.has_value(): true
 a1 = 42
 a1.has_value(): false
 a2.has_value(): true
 a2 = "Milky Way"
 a2.has_value(): false

See also
   reset destroys contained object
         (public member function)