The variant_associative_view describes a class that refers to an associative container (e.g: std::map) inside a variant. More...

#include <variant_associative_view.h>

Classes
class	const_iterator
	The variant_associative_view::const_iterator allows iteration over an associative container in a variant. More...

Public Member Functions
	variant_associative_view ()
	Constructs an invalid variant_associative_view object. More...

	variant_associative_view (const variant_associative_view &other)
	Constructs a copy of the given variant_associative_view `other`. More...

	~variant_associative_view () noexcept
	Destroys the variant_associative_view. More...

const_iterator	begin () const
	Returns an iterator to the first element of the container. More...

void	clear ()
	Removes all elements from the container. More...

const_iterator	end () const
	Returns an iterator to the element following the last element of the container. More...

std::pair< const_iterator, const_iterator >	equal_range (argument key)
	Returns a range containing all elements with the given `key` in the container. More...

std::size_t	erase (argument key)
	Removes the element (if one exists) with the key equivalent to `key`. More...

const_iterator	find (argument key)
	Finds an element with specific key `key` . More...

type	get_key_type () const noexcept
	Returns the type from the key of this associative container. More...

std::size_t	get_size () const noexcept
	Returns the number of elements in the associative container. More...

type	get_type () const noexcept
	Returns the type object of this associative container. More...

type	get_value_type () const noexcept
	Returns the type object from the value of this associative container. More...

std::pair< const_iterator, bool >	insert (argument key)
	Insert a key into the container. More...

std::pair< const_iterator, bool >	insert (argument key, argument value)
	Insert a key-value pair into the container. More...

bool	is_empty () const noexcept
	Checks if the container has no elements. More...

bool	is_key_only_type () const noexcept
	Returns `true`, when this associative container stores only keys. More...

bool	is_valid () const noexcept
	Returns true if this variant_associative_view is valid, that means the object is holding some data. More...

	operator bool () const noexcept
	Convenience function to check if this variant_associative_view is valid or not. More...

variant_associative_view &	operator= (const variant_associative_view &other) noexcept
	Assigns the value of the other variant_associative_view to this variant_associative_view. More...

void	swap (variant_associative_view &other) noexcept
	Swaps this variant_associative_view with the other variant_associative_view. More...

Detailed Description

The variant_associative_view describes a class that refers to an associative container (e.g: std::map) inside a variant.

With an instance of that class you can set/get values of such container, without having access to the type declaration of the type or it's elements.

A variant_associative_view can be created directly from a variant with its member function create_associative_view().

Remarks: The instance of an variant_associative_view is always valid as long as the referenced variant is valid, otherwise accessing a variant_associative_view is undefined behaviour.

Meta Information

RTTR recognize whether a type is an associative container or not with the help of the associative_container_mapper class template. This call can access different container types via one common interface. At the moment there exist specializations for following types: std::set<Key>, std::map<Key, T>, std::multiset<Key>, std::multimap<Key, T>, std::unordered_set<Key>, std::unordered_map<Key, T>, std::unordered_multiset<Key> and std::unordered_multimap<Key, T>.

Copying and Assignment

A variant_associative_view object can be copied and assigned, however each copy will reference the data of same underlying variant value.

Typical Usage

std::map<int, std::string> my_map = { { 1, "one" }, { 2, "two" }, { 3, "three" } };
variant var = my_map;
if (var.is_associative_container())
{
    variant_associative_view view = var.create_associative_view();
    std::cout << view.get_size() << std::endl;      // prints: '3'
    for (const auto& item : view)
    {
        // remark that the key and value are stored inside a 'std::reference_wrapper'
        std::cout << "Key: " << item.first.extract_wrapped_value().to_string() << " ";
        std::cout << "Value: " << item.second.extract_wrapped_value().to_string() << std::endl;
    }
}

See also: variant

Constructor & Destructor Documentation

rttr::variant_associative_view::variant_associative_view ( )

Constructs an invalid variant_associative_view object.

See also: is_valid()

rttr::variant_associative_view::variant_associative_view ( const variant_associative_view & other )

Constructs a copy of the given variant_associative_view other.

rttr::variant_associative_view::~variant_associative_view ( )

noexcept

Destroys the variant_associative_view.

Remarks: The underlying data is not destroyed.

Member Function Documentation

const_iterator rttr::variant_associative_view::begin ( ) const

Returns an iterator to the first element of the container.

See also: end()

Returns: Iterator to the first element .

void rttr::variant_associative_view::clear ( )

Removes all elements from the container.

Remarks: Invalidates all references, pointers, or iterators referring to contained elements.

const_iterator rttr::variant_associative_view::end ( ) const

Returns an iterator to the element following the last element of the container.

See also: begin()

Returns: Iterator to the element following the last element.

std::pair<const_iterator, const_iterator> rttr::variant_associative_view::equal_range ( argument key )

Returns a range containing all elements with the given key in the container.

Example code:

auto multimap = std::multimap<int, std::string>{ { 1, "A" }, { 2, "B" },  { 2, "C"}, { 2, "D" },
                                                 { 3, "E" }, { 3, "F" } };
variant var = multimap;
auto view = var.create_associative_view();
for (int i = 1; i <= 3; ++i)
{
    std::cout << i << " =>";
    auto range = view.equal_range(i);
    for (auto itr = range.first; itr != range.second; ++itr)
    {
        std::cout << " " << itr.value().extract_wrapped_value().to_string();
    }
    std::cout << std::endl;
}

Output:

=> A
=> B C D
=> E, F

Returns: std::pair containing a pair of iterators defining the wanted range: the first pointing to the first element that is not less than key and the second pointing to the first element greater than key.

std::size_t rttr::variant_associative_view::erase ( argument key )

Removes the element (if one exists) with the key equivalent to key.

Returns: The number of elements removed.

const_iterator rttr::variant_associative_view::find ( argument key )

Finds an element with specific key key .

Returns: The element with key equivalent to key. If no element is found an invalid iterator is returned.

type rttr::variant_associative_view::get_key_type ( ) const

noexcept

Returns the type from the key of this associative container.

Remarks: When the view is not valid, this function will return an invalid type object.

Returns: Type from the key of the associative container.

std::size_t rttr::variant_associative_view::get_size ( ) const

noexcept

Returns the number of elements in the associative container.

Returns: The number of elements in the associative container.

type rttr::variant_associative_view::get_type ( ) const

noexcept

Returns the type object of this associative container.

Remarks: When the view is not valid, this function will return an invalid type object.

Returns: Type of the associative container.

type rttr::variant_associative_view::get_value_type ( ) const

noexcept

Returns the type object from the value of this associative container.

Remarks: When the view is not valid, this function will return an invalid type object.

Returns: Type from the value of the associative container.

std::pair<const_iterator, bool> rttr::variant_associative_view::insert ( argument key )

Insert a key into the container.

Returns: A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool denoting whether the insertion took place.

std::pair<const_iterator, bool> rttr::variant_associative_view::insert	(	argument	key,
		argument	value
	)

Insert a key-value pair into the container.

Returns: A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool denoting whether the insertion took place.

bool rttr::variant_associative_view::is_empty ( ) const

noexcept

Checks if the container has no elements.

Returns: true if container is empty, otherwise false.

bool rttr::variant_associative_view::is_key_only_type ( ) const

noexcept

Returns true, when this associative container stores only keys.

When also value are stored, it will return false.

For example an std::set has no values, it's a key-only associative container. Then this method returns true. An std::map<K,V> on the other hand contains keys and values. So this method will then return false. A simple convenience method instead of calling: get_value_type().is_valid() == false;

Returns: true, when this associative container stores only keys; otherwise false.

bool rttr::variant_associative_view::is_valid ( ) const

noexcept

Returns true if this variant_associative_view is valid, that means the object is holding some data.

When the variant_associative_view doesn't hold any data it will return false.

Returns: True if this variant_associative_view is valid, otherwise false.

rttr::variant_associative_view::operator bool ( ) const

explicitnoexcept

Convenience function to check if this variant_associative_view is valid or not.

See also: is_valid()

Returns: True if this variant_associative_view is valid, otherwise false.

variant_associative_view& rttr::variant_associative_view::operator= ( const variant_associative_view & other )

noexcept

Assigns the value of the other variant_associative_view to this variant_associative_view.

Returns: A reference to the variant_associative_view with the new data.

void rttr::variant_associative_view::swap ( variant_associative_view & other )

noexcept

Swaps this variant_associative_view with the other variant_associative_view.

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

variant_associative_view.h

Classes

Public Member Functions

Detailed Description

Meta Information

Copying and Assignment

Typical Usage

Constructor & Destructor Documentation

Member Function Documentation