entt::basic_observer< Entity > Class Template Reference

Observer. More...

#include <observer.hpp>

Public Types
using	entity_type = Entity
	Underlying entity identifier.
using	size_type = std::size_t
	Unsigned integer type.
using	iterator = typename basic_sparse_set< Entity >::iterator
	Random access iterator type.

Public Member Functions
	basic_observer ()
	Default constructor.
	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 (basic_registry< entity_type > &reg, basic_collector< Matcher... >)
	Creates an observer and connects it to a given registry. More...
	~basic_observer ()=default
	Default destructor.
basic_observer &	operator= (const basic_observer &)=delete
	Default copy assignment operator, deleted on purpose. More...
basic_observer &	operator= (basic_observer &&)=delete
	Default move assignment operator, deleted on purpose. More...
template<typename... Matcher>
void	connect (basic_registry< entity_type > &reg, basic_collector< Matcher... >)
	Connects an observer to a given registry. More...
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. More...
bool	empty () const noexcept
	Checks whether an observer is empty. More...
const entity_type *	data () const noexcept
	Direct access to the list of entities of the observer. More...
iterator	begin () const noexcept
	Returns an iterator to the first entity of the observer. More...
iterator	end () const noexcept
	Returns an iterator that is past the last entity of the observer. More...
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. More...
template<typename Func >
void	each (Func func)
	Iterates entities and applies the given function object to them, then clears the observer. More...

Detailed Description

template<typename Entity>
class entt::basic_observer< Entity >

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 components.

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 components 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 components are created and assigned to entities.
• The entity currently pointed is modified (as an example, if one of the given components 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 components in any way invalidates all the iterators and using them results in undefined behavior.

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

Entity

A valid entity type (see entt_traits for more details).

Definition at line 172 of file observer.hpp.

Constructor & Destructor Documentation

basic_observer()

template<typename Entity >

template<typename... Matcher>

entt::basic_observer< Entity >::basic_observer ( basic_registry< entity_type > &  reg, basic_collector< Matcher... >    )

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.

Definition at line 298 of file observer.hpp.

Member Function Documentation

begin()

template<typename Entity >

iterator entt::basic_observer< Entity >::begin ( ) const

inlinenoexcept

Returns an iterator to the first entity of the observer.

The returned iterator points to the first entity of the observer. If the container is empty, the returned iterator will be equal to end().

Returns

An iterator to the first entity of the observer.

Definition at line 379 of file observer.hpp.

connect()

template<typename Entity >

template<typename... Matcher>

void entt::basic_observer< Entity >::connect ( basic_registry< entity_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 325 of file observer.hpp.

data()

template<typename Entity >

const entity_type* entt::basic_observer< Entity >::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 367 of file observer.hpp.

each() [1/2]

template<typename Entity >

template<typename Func >

void entt::basic_observer< Entity >::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 432 of file observer.hpp.

each() [2/2]

template<typename Entity >

template<typename Func >

void entt::basic_observer< Entity >::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);

Template Parameters

Func	Type of the function object to invoke.

Parameters

func	A valid function object.

Definition at line 416 of file observer.hpp.

empty()

template<typename Entity >

bool entt::basic_observer< Entity >::empty ( ) const

inlinenoexcept

Checks whether an observer is empty.

Returns

True if the observer is empty, false otherwise.

Definition at line 351 of file observer.hpp.

end()

template<typename Entity >

iterator entt::basic_observer< Entity >::end ( ) const

inlinenoexcept

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

The returned iterator points to the entity following the last entity of the observer. Attempting to dereference the returned iterator results in undefined behavior.

Returns

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

Definition at line 393 of file observer.hpp.

operator=() [1/2]

template<typename Entity >

basic_observer& entt::basic_observer< Entity >::operator= ( basic_observer< Entity > &&  )

delete

Default move assignment operator, deleted on purpose.

Returns

This observer.

operator=() [2/2]

template<typename Entity >

basic_observer& entt::basic_observer< Entity >::operator= ( const basic_observer< Entity > &  )

delete

Default copy assignment operator, deleted on purpose.

Returns

This observer.

size()

template<typename Entity >

size_type entt::basic_observer< Entity >::size ( ) const

inlinenoexcept

Returns the number of elements in an observer.

Returns

Number of elements.

Definition at line 343 of file observer.hpp.

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

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