std::any::has_value

 

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std::any

Member functions

any::any

any::~any

any::operator=

Modifiers

any::emplace

any::reset

any::swap

Observers

any::has_value

any::type

Non-member functions

swap(std::any)

any_cast

make_any

 

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)