Defined in header <ranges> | ||
|---|---|---|
template< ranges::range R >
requires std::movable<R> && (!/*is-initializer-list*/<R>)
class owning_view :
public ranges::view_interface<owning_view<R>>
| (since C++20) |
owning_view is a view that has unique ownership of a range. It is move-only and stores that range within it.
The constant /*is-initializer-list*/<R> in the requires-clause is true if and only if std::remove_cvref_t<R> is a specialization of std::initializer_list.
Typical implementations of owning_view have only one non-static data member: the underlying range of type R. The member is shown as r_ here (the name is exposition-only).
|
(C++20) | constructs an owning_view by value-initializing or move-constructing the stored range (public member function) |
|
(C++20) | move-assigns the stored range (public member function) |
|
(C++20) | returns a reference to the stored range (public member function) |
|
(C++20) | returns the beginning iterator of the stored range (public member function) |
|
(C++20) | returns the sentinel of the stored range (public member function) |
|
(C++20) | checks whether the stored range is empty (public member function) |
|
(C++20) | returns the size of the stored sized_range (public member function) |
|
(C++20) | returns the pointer to the beginning of the stored contiguous_range (public member function) |
Inherited from |
|
|
(C++23) | returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>) |
|
(C++23) | returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>) |
owning_view() requires std::default_initializable<R> = default; | (1) | (since C++20) |
owning_view( owning_view&& other ) = default; | (2) | (since C++20) |
constexpr owning_view( R&& t ); | (3) | (since C++20) |
owning_view( const owning_view& ) = delete; | (4) | (since C++20) |
= R()).other.t.owning_view is move-only.| other | - | another owning_view to move from |
| t | - | range to move from |
owning_view& operator=( owning_view&& other ) = default; | (1) | (since C++20) |
owning_view& operator=( const owning_view& ) = delete; | (2) | (since C++20) |
other.owning_view is move-only.| other | - | another owning_view to move from |
*this.
constexpr R& base() & noexcept; | (1) | (since C++20) |
constexpr const R& base() const & noexcept; | (2) | (since C++20) |
constexpr R&& base() && noexcept; | (3) | (since C++20) |
constexpr const R&& base() const && noexcept; | (4) | (since C++20) |
Returns a reference to the stored range, keeping value category and const-qualification.
return r_;.return std::move(r_);. constexpr ranges::iterator_t<R> begin(); | (1) | (since C++20) |
constexpr auto begin() const requires ranges::range<const R>; | (2) | (since C++20) |
Equivalent to return ranges::begin(r_);.
constexpr ranges::sentinel_t<R> end(); | (1) | (since C++20) |
constexpr auto end() const requires ranges::range<const R>; | (2) | (since C++20) |
Equivalent to return ranges::end(r_);.
constexpr bool empty() requires requires { ranges::empty(r_); };
| (1) | (since C++20) |
constexpr bool empty() const requires requires { ranges::empty(r_); };
| (2) | (since C++20) |
Equivalent to return ranges::empty(r_);.
constexpr auto size() requires ranges::sized_range<R>; | (1) | (since C++20) |
constexpr auto size() const requires ranges::sized_range<const R>; | (2) | (since C++20) |
Equivalent to return ranges::size(r_);.
constexpr auto data() requires ranges::contiguous_range<R>; | (1) | (since C++20) |
constexpr auto data() const requires ranges::contiguous_range<const R>; | (2) | (since C++20) |
Equivalent to return ranges::data(r_);.
template< class T >
inline constexpr bool enable_borrowed_range<std::ranges::owning_view<T>> =
std::ranges::enable_borrowed_range<T>;
| (since C++20) |
This specialization of std::ranges::enable_borrowed_range makes owning_view satisfy borrowed_range when the underlying range satisfies it.
#include <cassert>
#include <iostream>
#include <ranges>
#include <string>
int main()
{
using namespace std::literals;
std::ranges::owning_view ov{ "cosmos"s }; // the deduced type of R is std::string;
// `ov` is the only owner of this string
assert(
ov.empty() == false and
ov.size() == 6 and
ov.size() == ov.base().size() and
ov.front() == 'c' and
ov.front() == *ov.begin() and
ov.back() == 's' and
ov.back() == *(ov.end() - 1) and
ov.data() == ov.base()
);
std::cout << "sizeof(ov): " << sizeof ov << '\n' // typically equal to sizeof(R)
<< "range-for: ";
for (const char ch: ov)
std::cout << ch;
std::cout << '\n';
std::ranges::owning_view<std::string> ov2;
assert(ov2.empty());
// ov2 = ov; // compile-time error: copy assignment operator is deleted
ov2 = std::move(ov); // OK
assert(ov2.size() == 6);
}Possible output:
sizeof(ov): 32 range-for: cosmos
|
(C++20) | a view of the elements of some other range (class template) |
|
(C++20) | a view that includes all elements of a range (alias template) (range adaptor object) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/ranges/owning_view