NAME

std::basic_string_view::empty - std::basic_string_view::empty

Synopsis

constexpr bool empty() const noexcept; (since C++17)
(until C++20)
[[nodiscard]] constexpr bool empty() const noexcept; (since C++20)

Checks if the view has no characters, i.e. whether size() == 0.

Parameters

(none)

Return value

true if the view is empty, false otherwise

Complexity

Constant.

Example

// Run this code

#include <string_view>
#include <iostream>

void check_string(std::string_view ref)
{
// Print a string surrounded by single quotes, its length
// and whether it is considered empty.
std::cout << std::boolalpha
<< "'" << ref << "' has " << ref.size()
<< " character(s); emptiness: " << ref.empty() << '\n';
}

int main(int argc, char **argv)
{
// An empty string
check_string("");

// Almost always not empty: argv[0]
if (argc > 0)
check_string(argv[0]);
}

Possible output:

'' has 0 character(s); emptiness: true
'./a.out' has 7 character(s); emptiness: false

See also

size returns the number of characters
length (public member function)
(C++17)
max_size returns the maximum number of characters
(C++17) (public member function)
size
ssize returns the size of a container or array
(C++17) (function template)
(C++20)
empty checks whether the container is empty
(C++17) (function template)
empty checks whether the string is empty
(public member function of std::basic_string<CharT,Traits,Allocator>)