std::optional-like wrapper around an object that is the source for a view: this may hold an object or not; and the wrapped object is owned by this object if the wrapped object's type satisfies std::ranges::view, and not owned otherwise. More...

#include <view_sources.h>

Inheritance diagram for mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >:

[legend]

Public Types
using	Source_t = Source_tp

using	Raw_source_t = Raw_view_source< Source_t, owns_source >
	Source_t if `owns_source`, otherwise `Source_t &`. More...

using	Optional_source_t = std::conditional_t< owns_source, std::optional< Source_t >, const Source_t * >
	Internal representation of the source. More...

Public Member Functions
	Optional_view_source ()=default
	Construct an objec that does not hold a source. More...

	Optional_view_source (const Source_t &source)
	Construct from a const reference to the source. More...

	Optional_view_source (const Source_t *source)
	Construct from a const pointer to the source. More...

bool	has_object () const
	Return true if this object holds a source. More...

const Raw_source_t &	get () const
	Return a copy of the stored object if it is owned; otherwise a reference to it. More...

const Raw_source_t &	reference () const
	Return a reference to the stored object. More...

const Source_t *	pointer () const
	Return a pointer to the source if there is one, or nullptr otherwise. More...

const Source_t *	operator-> () const
	Arrow operator to access members of the source. More...

auto	begin () const
	Return a valid begin iterator, even if !has_object(). More...

auto	end () const
	Return a valid end iterator, even if !has_object(). More...

Static Public Attributes
static constexpr bool	owns_source = owns_source_tp
	True if this object owns a copy of its source; false if it holds a reference to its source. More...

Static Protected Member Functions
static auto	null_iterator ()

Static Private Member Functions
static decltype(auto)	from_ptr (const Source_t *object)
	Return an `Optional_source_t` from the given pointer, holding no object if the pointer is nullptr, and holding the pointed-to object otherwise. More...

Private Attributes
Optional_source_t	m_source {}
	The source. More...

Detailed Description

template<class Source_tp, bool owns_source_tp = std::ranges::view<Source_tp>>
class mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >

std::optional-like wrapper around an object that is the source for a view: this may hold an object or not; and the wrapped object is owned by this object if the wrapped object's type satisfies std::ranges::view, and not owned otherwise.

This is meant to be used by member variables of the view class, or the view's iterator class, that need to reference the source.

This intends to prevent dangling references by enforcing the following rule:

"Views and their iterators shall represent sources that are views by-value, and sources that are containers by-reference."

For full justification, see readme.md.

Internally, this class stores a source of type T using a member variable of type std::optional<T> if std::ranges::view<T>, or type const T * otherwise. It provides an API similar to std::optional.

Note that types need to be declared explicitly as views, using either std::ranges::view_base or std::ranges::enable_range.

Template Parameters

Source_tp	The source type.
owns_source_tp	Determines if the object owns its source. By default, this is deduced from `std::ranges::view<Source_tp>`.

Member Typedef Documentation

◆ Optional_source_t

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

using mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Optional_source_t = std::conditional_t<owns_source, std::optional<Source_t>, const Source_t *>

Internal representation of the source.

◆ Raw_source_t

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

using mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Raw_source_t = Raw_view_source<Source_t, owns_source>

Source_t if owns_source, otherwise Source_t &.

◆ Source_t

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

using mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Source_t = Source_tp

Constructor & Destructor Documentation

◆ Optional_view_source() [1/3]

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Optional_view_source ( )

default

Construct an objec that does not hold a source.

◆ Optional_view_source() [2/3]

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Optional_view_source ( const Source_t & source )

inlineexplicit

Construct from a const reference to the source.

◆ Optional_view_source() [3/3]

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::Optional_view_source ( const Source_t * source )

inlineexplicit

Construct from a const pointer to the source.

The source may be nullptr, in which case this object will not hold any sourcd.

Member Function Documentation

◆ begin()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

auto mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::begin ( ) const

inline

Return a valid begin iterator, even if !has_object().

If !has_object(), it is defined that the source is an empty range, so then this function returns the end iterator to a default-constructed source.

This requires std::ranges::common_range<Source_t>, i.e., begin() and end() must return the same type.

◆ end()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

auto mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::end ( ) const

inline

Return a valid end iterator, even if !has_object().

If !has_object(), this returns the end iterator to a default-constructed source.

◆ from_ptr()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

static decltype(auto) mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::from_ptr ( const Source_t * object )

inlinestaticprivate

Return an Optional_source_t from the given pointer, holding no object if the pointer is nullptr, and holding the pointed-to object otherwise.

◆ get()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

const Raw_source_t & mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::get ( ) const

inline

Return a copy of the stored object if it is owned; otherwise a reference to it.

The behavior is undefined if !has_object().

◆ has_object()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

bool mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::has_object ( ) const

inline

Return true if this object holds a source.

◆ null_iterator()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

static auto mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::null_iterator ( )

inlinestaticprotected

◆ operator->()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

const Source_t * mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::operator-> ( ) const

inline

Arrow operator to access members of the source.

The behavior is undefined if !has_object().

Note: To access begin/end iterators from the source when there is a source, and objects that behave like end iterators when there is no source, use o.begin() and o.end() instead of o->begin() and o->end().

◆ pointer()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

const Source_t * mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::pointer ( ) const

inline

Return a pointer to the source if there is one, or nullptr otherwise.

Note that the pointer is only valid as long as this object exists.

◆ reference()

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

const Raw_source_t & mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::reference ( ) const

inline

Return a reference to the stored object.

The behavior is undefined if !has_object(). Note that the reference is only valid as long as this object exists.

Member Data Documentation

◆ m_source

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

Optional_source_t mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::m_source {}

private

The source.

◆ owns_source

template<class Source_tp , bool owns_source_tp = std::ranges::view<Source_tp>>

constexpr bool mysql::ranges::Optional_view_source< Source_tp, owns_source_tp >::owns_source = owns_source_tp

staticconstexpr

True if this object owns a copy of its source; false if it holds a reference to its source.

The documentation for this class was generated from the following file:

libs/mysql/ranges/view_sources.h

Public Types

Public Member Functions

Static Public Attributes

Static Protected Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

◆ Optional_source_t

◆ Raw_source_t

◆ Source_t

Constructor & Destructor Documentation

◆ Optional_view_source() [1/3]

◆ Optional_view_source() [2/3]

◆ Optional_view_source() [3/3]

Member Function Documentation

◆ begin()

◆ end()

◆ from_ptr()

◆ get()

◆ has_object()

◆ null_iterator()

◆ operator->()

◆ pointer()

◆ reference()

Member Data Documentation

◆ m_source

◆ owns_source