std::ranges::owning_view
From cppreference.com
| Defined in header <ranges>
|
||
| template< ranges::range R > requires std::movable<R> && (!/*is-initializer-list*/<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.
[edit] Data members
| Member | Description |
R r_
|
the underlying range (exposition-only member object*) |
[edit] Member functions
constructs an owning_view by value-initializing or move-constructing the stored range (public member function) | |
| move-assigns the stored range (public member function) | |
| returns a reference to the stored range (public member function) | |
| returns the beginning iterator of the stored range (public member function) | |
| returns the sentinel of the stored range (public member function) | |
| checks whether the stored range is empty (public member function) | |
returns the size of the stored sized_range (public member function) | |
| (C++26) |
returns the approximate size of the stored approximately_sized_range (public member function) |
returns the pointer to the beginning of the stored contiguous_range (public member function) | |
Inherited from std::ranges::view_interface | |
| (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>)
|
| returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface<D>)
| |
returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface<D>)
| |
returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range (public member function of std::ranges::view_interface<D>)
| |
returns the nth element in the derived view, provided only if it satisfies random_access_range (public member function of std::ranges::view_interface<D>)
| |
std::ranges::owning_view::owning_view
| 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) |
Parameters
| other | - | another owning_view to move from
|
| t | - | range to move from |
Notes
owning_view does not explicitly define a copy constructor. owning_view is move-only.
std::ranges::owning_view::operator=
| owning_view& operator=( owning_view&& other ) = default; |
(since C++20) | |
Move assignment operator. Move assigns r_ from that of other.
Parameters
| other | - | another owning_view to move from
|
Return value
*this
Notes
owning_view does not explicitly define a copy assignment operator. owning_view is move-only.
std::ranges::owning_view::base
| 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 value
1,2)
r_3,4) std::move(
r_ )
std::ranges::owning_view::begin
| constexpr ranges::iterator_t<R> begin(); |
(1) | (since C++20) |
| constexpr auto begin() const requires ranges::range<const R>; |
(2) | (since C++20) |
Returns ranges::begin(r_ ).
std::ranges::owning_view::end
| constexpr ranges::sentinel_t<R> end(); |
(1) | (since C++20) |
| constexpr auto end() const requires ranges::range<const R>; |
(2) | (since C++20) |
Returns ranges::end(r_ ).
std::ranges::owning_view::empty
| 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) |
Returns ranges::empty(r_ ).
std::ranges::owning_view::size
| 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) |
Returns ranges::size(r_ ).
std::ranges::owning_view::reserve_hint
| constexpr auto reserve_hint() requires ranges::approximately_sized_range<R>; |
(1) | (since C++26) |
| constexpr auto reserve_hint() const requires ranges::approximately_sized_range<const R>; |
(2) | (since C++26) |
Returns ranges::reserve_hint(r_ ).
std::ranges::owning_view::data
| 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) |
Returns ranges::data(r_ ).
[edit] Helper templates
| template< class T > constexpr bool enable_borrowed_range<std::ranges::owning_view<T>> = |
(since C++20) | |
This specialization of ranges::enable_borrowed_range makes owning_view satisfy borrowed_range when the underlying range satisfies it.
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_ranges_reserve_hint |
202502L |
(C++26) | ranges::approximately_sized_range and reserve_hint
|
[edit] Example
Run this code
#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 && ov.size() == 6 && ov.size() == ov.base().size() && ov.front() == 'c' && ov.front() == *ov.begin() && ov.back() == 's' && ov.back() == *(ov.end() - 1) && 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
[edit] See also
| (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) |
