std::basic_string_view<CharT,Traits>::empty

From cppreference.com
 
 
 
 
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

#include <iostream>
#include <string_view>
 
// Print a string surrounded by single quotes, its
// length and whether it is considered empty.
void check_string(std::string_view ref)
{
    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

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