Observer. More...

#include <observer.hpp>

Public Types
using	allocator_type = Allocator
	Allocator type.

using	registry_type = Registry

using	entity_type = typename registry_type::entity_type
	Underlying entity identifier.

using	size_type = std::size_t
	Unsigned integer type.

using	iterator = typename registry_type::common_type::iterator
	Random access iterator type.

Public Member Functions
	basic_observer ()
	Default constructor.

	basic_observer (const allocator_type &allocator)
	Constructs an empty storage with a given allocator.

	basic_observer (const basic_observer &)=delete
	Default copy constructor, deleted on purpose.

	basic_observer (basic_observer &&)=delete
	Default move constructor, deleted on purpose.

template<typename... Matcher>
	basic_observer (registry_type &reg, basic_collector< Matcher... >, const allocator_type &allocator=allocator_type{})
	Creates an observer and connects it to a given registry.

	~basic_observer ()=default
	Default destructor.

basic_observer &	operator= (const basic_observer &)=delete
	Default copy assignment operator, deleted on purpose.

basic_observer &	operator= (basic_observer &&)=delete
	Default move assignment operator, deleted on purpose.

template<typename... Matcher>
void	connect (registry_type &reg, basic_collector< Matcher... >)
	Connects an observer to a given registry.

void	disconnect ()
	Disconnects an observer from the registry it keeps track of.

size_type	size () const noexcept
	Returns the number of elements in an observer.

bool	empty () const noexcept
	Checks whether an observer is empty.

const entity_type *	data () const noexcept
	Direct access to the list of entities of the observer.

iterator	begin () const noexcept
	Returns an iterator to the first entity of the observer.

iterator	end () const noexcept
	Returns an iterator that is past the last entity of the observer.

void	clear () noexcept
	Clears the underlying container.

template<typename Func >
void	each (Func func) const
	Iterates entities and applies the given function object to them.

template<typename Func >
void	each (Func func)
	Iterates entities and applies the given function object to them, then clears the observer.

Detailed Description

template<typename Registry, typename Allocator>
class entt::basic_observer< Registry, Allocator >

Observer.

An observer returns all the entities and only the entities that fit the requirements of at least one matcher. Moreover, it's guaranteed that the entity list is tightly packed in memory for fast iterations.
In general, observers don't stay true to the order of any set of elements.

Observers work mainly with two types of matchers, provided through a collector:

Observing matcher: an observer will return at least all the living entities for which one or more of the given elements have been updated and not yet destroyed.
Grouping matcher: an observer will return at least all the living entities that would have entered the given group if it existed and that would have not yet left it.

If an entity respects the requirements of multiple matchers, it will be returned once and only once by the observer in any case.

Matchers support also filtering by means of a where clause that accepts both a list of types and an exclusion list.
Whenever a matcher finds that an entity matches its requirements, the condition of the filter is verified before to register the entity itself. Moreover, a registered entity isn't returned by the observer if the condition set by the filter is broken in the meantime.

Important

Iterators aren't invalidated if:

New instances of the given elements are created and assigned to entities.
The entity currently pointed is modified (as an example, if one of the given elements is removed from the entity to which the iterator points).
The entity currently pointed is destroyed.

In all the other cases, modifying the pools of the given elements in any way invalidates all the iterators.

Warning: Lifetime of an observer doesn't necessarily have to overcome that of the registry to which it is connected. However, the observer must be disconnected from the registry before being destroyed to avoid crashes due to dangling pointers.

Template Parameters

Registry	Basic registry type.
Allocator	Type of allocator used to manage memory and elements.

Definition at line 160 of file observer.hpp.

Member Typedef Documentation

◆ allocator_type

template<typename Registry , typename Allocator >

using entt::basic_observer< Registry, Allocator >::allocator_type = Allocator

Allocator type.

Definition at line 257 of file observer.hpp.

◆ entity_type

template<typename Registry , typename Allocator >

using entt::basic_observer< Registry, Allocator >::entity_type = typename registry_type::entity_type

Underlying entity identifier.

Definition at line 261 of file observer.hpp.

◆ iterator

template<typename Registry , typename Allocator >

using entt::basic_observer< Registry, Allocator >::iterator = typename registry_type::common_type::iterator

Random access iterator type.

Definition at line 265 of file observer.hpp.

◆ registry_type

template<typename Registry , typename Allocator >

using entt::basic_observer< Registry, Allocator >::registry_type = Registry

Basic registry type.

Definition at line 259 of file observer.hpp.

◆ size_type

template<typename Registry , typename Allocator >

using entt::basic_observer< Registry, Allocator >::size_type = std::size_t

Unsigned integer type.

Definition at line 263 of file observer.hpp.

Constructor & Destructor Documentation

◆ basic_observer() [1/3]

template<typename Registry , typename Allocator >

entt::basic_observer< Registry, Allocator >::basic_observer ( )

inline

Default constructor.

Definition at line 268 of file observer.hpp.

◆ basic_observer() [2/3]

template<typename Registry , typename Allocator >

entt::basic_observer< Registry, Allocator >::basic_observer ( const allocator_type & allocator )

inlineexplicit

Constructs an empty storage with a given allocator.

Parameters

allocator The allocator to use.

Definition at line 275 of file observer.hpp.

◆ basic_observer() [3/3]

template<typename Registry , typename Allocator >

template<typename... Matcher>

entt::basic_observer< Registry, Allocator >::basic_observer	(	registry_type &	reg,
		basic_collector< Matcher... >	,
		const allocator_type &	allocator = allocator_type{} )

inline

Creates an observer and connects it to a given registry.

Template Parameters

Matcher Types of matchers to use to initialize the observer.

Parameters

reg	A valid reference to a registry.
allocator	The allocator to use.

Definition at line 293 of file observer.hpp.

Member Function Documentation

◆ begin()

template<typename Registry , typename Allocator >

iterator entt::basic_observer< Registry, Allocator >::begin ( ) const

inlinenoexcept

Returns an iterator to the first entity of the observer.

If the observer is empty, the returned iterator will be equal to end().

Returns: An iterator to the first entity of the observer.

Definition at line 377 of file observer.hpp.

◆ clear()

template<typename Registry , typename Allocator >

void entt::basic_observer< Registry, Allocator >::clear ( )

inlinenoexcept

Clears the underlying container.

Definition at line 391 of file observer.hpp.

◆ connect()

template<typename Registry , typename Allocator >

template<typename... Matcher>

void entt::basic_observer< Registry, Allocator >::connect	(	registry_type &	reg,
		basic_collector< Matcher... >	)

inline

Connects an observer to a given registry.

Template Parameters

Matcher Types of matchers to use to initialize the observer.

Parameters

reg	A valid reference to a registry.

Definition at line 321 of file observer.hpp.

◆ data()

template<typename Registry , typename Allocator >

const entity_type * entt::basic_observer< Registry, Allocator >::data ( ) const

inlinenoexcept

Direct access to the list of entities of the observer.

The returned pointer is such that range [data(), data() + size()) is always a valid range, even if the container is empty.

Note: Entities are in the reverse order as returned by the begin/end iterators.

Returns: A pointer to the array of entities.

Definition at line 366 of file observer.hpp.

◆ disconnect()

template<typename Registry , typename Allocator >

void entt::basic_observer< Registry, Allocator >::disconnect ( )

inline

Disconnects an observer from the registry it keeps track of.

Definition at line 331 of file observer.hpp.

◆ each() [1/2]

template<typename Registry , typename Allocator >

template<typename Func >

void entt::basic_observer< Registry, Allocator >::each ( Func func )

inline

Iterates entities and applies the given function object to them, then clears the observer.

See also: each

Template Parameters

Func	Type of the function object to invoke.

Parameters

func	A valid function object.

Definition at line 425 of file observer.hpp.

◆ each() [2/2]

template<typename Registry , typename Allocator >

template<typename Func >

void entt::basic_observer< Registry, Allocator >::each ( Func func ) const

inline

Iterates entities and applies the given function object to them.

The function object is invoked for each entity.
The signature of the function must be equivalent to the following form:

void(const entity_type);

entt::basic_observer::entity_type

typename registry_type::entity_type entity_type

Underlying entity identifier.

Definition observer.hpp:261

entt::make_obj_using_allocator

constexpr Type make_obj_using_allocator(const Allocator &allocator, Args &&...args)

Uses-allocator construction utility (waiting for C++20).

Definition memory.hpp:219

Template Parameters

Func	Type of the function object to invoke.

Parameters

func	A valid function object.

Definition at line 409 of file observer.hpp.

◆ empty()

template<typename Registry , typename Allocator >

bool entt::basic_observer< Registry, Allocator >::empty ( ) const

inlinenoexcept

Checks whether an observer is empty.

Returns: True if the observer is empty, false otherwise.

Definition at line 350 of file observer.hpp.

◆ end()

template<typename Registry , typename Allocator >

iterator entt::basic_observer< Registry, Allocator >::end ( ) const

inlinenoexcept

Returns an iterator that is past the last entity of the observer.

Returns: An iterator to the entity following the last entity of the observer.

Definition at line 386 of file observer.hpp.

◆ operator=() [1/2]

template<typename Registry , typename Allocator >

basic_observer & entt::basic_observer< Registry, Allocator >::operator= ( basic_observer< Registry, Allocator > && )

delete

Default move assignment operator, deleted on purpose.

Returns: This observer.

◆ operator=() [2/2]

template<typename Registry , typename Allocator >

basic_observer & entt::basic_observer< Registry, Allocator >::operator= ( const basic_observer< Registry, Allocator > & )

delete

Default copy assignment operator, deleted on purpose.

Returns: This observer.

◆ size()

template<typename Registry , typename Allocator >

size_type entt::basic_observer< Registry, Allocator >::size ( ) const

inlinenoexcept

Returns the number of elements in an observer.

Returns: Number of elements.

Definition at line 342 of file observer.hpp.

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

src/entt/entity/fwd.hpp
src/entt/entity/observer.hpp

Public Types

Public Member Functions

Detailed Description

Member Typedef Documentation

◆ allocator_type

◆ entity_type

◆ iterator

◆ registry_type

◆ size_type

Constructor & Destructor Documentation

◆ basic_observer() [1/3]

◆ basic_observer() [2/3]

◆ basic_observer() [3/3]

Member Function Documentation

◆ begin()

◆ clear()

◆ connect()

◆ data()

◆ disconnect()

◆ each() [1/2]

◆ each() [2/2]

◆ empty()

◆ end()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ size()