std::string_view size() method

od C++17

// Const version only
constexpr size_type size() const noexcept;

// Const version only
constexpr size_type length() const noexcept;

Returns the number of elements (CharTs) in the container, i.e. std::distance(begin(), end()).

Parameters

(none)

Return value

The number of elements (CharTs) in the container.

Complexity

Constant - O(1).

Notes

For std::string_view, the elements are bytes (objects of type char), which are not the same as characters if a multibyte encoding such as UTF-8 is used.

Example

Main.cpp

#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