std::basic_string_view<CharT,Traits>::basic_string_view - cppreference.com (original) (raw)

constexpr basic_string_view() noexcept;	(1)	(since C++17)
constexpr basic_string_view( const basic_string_view& other ) noexcept = default;	(2)	(since C++17)
constexpr basic_string_view( const CharT* s, size_type count );	(3)	(since C++17)
constexpr basic_string_view( const CharT* s );	(4)	(since C++17)
template< class It, class End > constexpr basic_string_view( It first, End last );	(5)	(since C++20)
template< class R > constexpr explicit basic_string_view( R&& r );	(6)	(since C++23)
basic_string_view( std::nullptr_t ) = delete;	(7)	(since C++23)

Default constructor. Constructs an empty std::basic_string_view. After construction, data() is equal to nullptr, and size() is equal to 0.
Copy constructor. Constructs a view of the same content as other. After construction, data() is equal to other.data(), and size() is equal to other.size().
Constructs a view of the first count characters of the character array starting with the element pointed by s. s can contain null characters. The behavior is undefined if [s, s + count) is not a valid range (even though the constructor may not access any of the elements of this range). After construction, data() is equal to s, and size() is equal to count.
Constructs a view of the null-terminated character string pointed to by s, not including the terminating null character. The length of the view is determined as if by Traits::length(s). The behavior is undefined if [s, s + Traits::length(s)) is not a valid range. After construction, data() is equal to s, and size() is equal to Traits::length(s).
std::basic_string_view cannot be constructed from nullptr.

[edit] Parameters

other	-	another view to initialize the view with
s	-	pointer to a character array or a C string to initialize the view with
count	-	number of characters to include in the view
first	-	iterator to the first character of the sequence
last	-	iterator past the last character of the sequence or another sentinel
r	-	a contiguous range that contains the sequence

[edit] Complexity

1-3,5,6) Constant.

Linear in length of s.

[edit] Example

#include #include #include #include #include int main() { std::string cppstr = "Foo"; std::string_view cppstr_v(cppstr); // overload (2), after // std:🧵:operator string_view std::cout << "1) cppstr_v: " << std::quoted(cppstr_v) << '\n'; char array[3] = {'B', 'a', 'r'}; std::string_view array_v(array, std::size(array)); // overload (3) std::cout << "2) array_v: " << std::quoted(array_v) << '\n'; const char* one_0_two = "One\0Two"; std::string_view one_two_v{one_0_two, 7}; // overload (3) std::cout << "3) one_two_v: ""; for (char c : one_two_v) std::cout << (c != '\0' ? c : '?'); std::cout << "", one_two_v.size(): " << one_two_v.size() << '\n'; std::string_view one_v{one_0_two}; // overload (4) std::cout << "4) one_v: " << std::quoted(one_v) << ", one_v.size(): " << one_v.size() << '\n'; constexpr std::wstring_view wcstr_v = L"xyzzy"; // overload (4) std::cout << "5) wcstr_v.size(): " << wcstr_v.size() << '\n'; std::array ar = {'P', 'u', 'b'}; std::string_view ar_v(ar.begin(), ar.end()); // overload (5), C++20 std::cout << "6) ar_v: " << std::quoted(ar_v) << '\n'; // std::string_view ar_v2{ar}; // overload (6), OK in C++23 // std::cout << "ar_v2: " << std::quoted(ar_v2) << '\n'; // ar_v2: "Pub" [[maybe_unused]] auto zero = [] { /* ... */ return nullptr; }; // std::string_view s{zero()}; // overload (7), won't compile since C++23 }

Output:

cppstr_v: "Foo"
array_v: "Bar"
one_two_v: "One?Two", one_two_v.size(): 7
one_v: "One", one_v.size(): 3
wcstr_v.size(): 5
ar_v: "Pub"

[edit] See also

| | assigns a view (public member function) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | constructs a basic_string (public member function of std::basic_string<CharT,Traits,Allocator>) [edit] |