std::string_view constructors

std::basic_string_view class can be constructed in many different ways. Use the button in the top-right corner to navigate with arrows for convenience.

Default constructor​

basic_string_view();

constexpr basic_string_view() noexcept;

Default constructor. Constructs an empty string view with:

• data() == nullptr
• size() == 0

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>
#include <iomanip>

int main() {
  // Default constructed string view
  std::string_view sv;

  std::cout << sv.size() << ' ' << std::quoted(sv);
}

0 ""

Defaulted copy constructor​

constexpr basic_string_view( const basic_string_view& other ) noexcept
    = default;

Copy constructor. Constructs a view of the same content as other, which has:

• data() == other.data()
• size() == other.size()

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>
#include <iomanip>

int main() {
  std::string_view sv = "Hello";
  std::string_view sv2 = sv;

  std::cout << sv.size() << ' ' << std::quoted(sv) << '\n';
  std::cout << sv2.size() << ' ' << std::quoted(sv2);
}

5 "Hello"
5 "Hello"

Char pointer constructor (bound)​

constexpr basic_string_view( const CharT* s, size_type count );

Constructs a view of the first count characters of the character array starting with the element pointed by s. The created view has:

• data() == s
• size() == count

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>
#include <iomanip>

int main() {
  std::string_view sv("Hello World!", 5);

  std::cout << sv.size() << ' ' << std::quoted(sv) << '\n';
}

5 "Hello"

Char pointer constructor (unbound)​

constexpr basic_string_view( const CharT* s );

• data() == s
• size() == Traits::length(s)

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>
#include <iomanip>

int main() {
  const char* string = "Hello\0 World!";
  std::string_view sv(string);

  std::cout << sv.size() << ' ' << std::quoted(sv) << '\n';
}

5 "Hello"

Copy range constructor (iterators)​

template< class It, class End >
constexpr basic_string_view( It first, End last );

Constructs a string view over the range [ first, last ). The resulting view has:

• data() == std::to_address(first)
• size() == last - first

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>

int main() {
  std::string s = "Hello World!";
  std::string_view sv(s.begin(), s.begin()+5);
  std::string_view sv2(s.begin() + 6, s.end());

  std::cout << sv << ' ' << sv2;
}

Hello World!

Copy range constructor (range)​

template< class R >
explicit constexpr basic_string_view( R&& r );

Constructs a string view over the range r. The resulting view has:

• data() == ranges::data(r)
• size() == ranges::size(r)

Complexity​

Constant - O(1).

Example​

#include <string_view>
#include <iostream>

int main() {
  std::string s = "Hello";
  std::string_view sv(s);

  std::cout << sv;
}

Hello

Deleted std::nullptr_t constructor​

constexpr basic_string_view( std::nullptr_t ) = delete;

A deleted constructor that prohibits constructing a string view from a nullptr.

Example​

#include <string_view>

int main() {
  // std::string_view sv(nullptr); // Won't compile!
}