bertini::Observable Class Reference

An abstract observable type, maintaining a list of observers, who can be notified in case of Events. More...

#include <observable.hpp>

Inheritance diagram for bertini::Observable:

Public Member Functions
virtual	~Observable ()=default
	Observable ()=default
	Observable (Observable const &)
	Copies do NOT inherit the watcher list: observers subscribed to the source object, not to the copy.
Observable &	operator= (Observable const &)
	Copy-assignment: leaves the target's own watcher list untouched (see the copy ctor note).
void	AddObserver (AnyObserver &new_observer) const
	Add an observer (non-owning) to observe this observable.
void	AddObserver (std::shared_ptr< AnyObserver > const &new_observer) const
	Add an observer whose lifetime is co-owned by this observable.
void	RemoveObserver (AnyObserver &observer) const
	Remove an observer from this observable.
virtual bool	ObservableIsA (std::type_index t) const
	Whether this observable may be observed as the given type.

Protected Member Functions
void	NotifyObservers (AnyEvent const &e) const
	Sends an event to observers that subscribed to its exact dynamic type, then to all catch-all (untyped) observers.
void	NotifyObservers (AnyEvent &e) const
	Notify all observers of a (mutable) event.
bool	HasObservers () const
	Whether anyone is currently observing (conservative).

Detailed Description

An abstract observable type, maintaining a list of observers, who can be notified in case of Events.

Some known observable types are Tracker and Endgame.

Constructor & Destructor Documentation

~Observable()

virtual bertini::Observable::~Observable ( )

virtualdefault

Observable() [1/2]

bertini::Observable::Observable ( )

default

Observable() [2/2]

bertini::Observable::Observable ( Observable const & )

inline

Copies do NOT inherit the watcher list: observers subscribed to the source object, not to the copy.

This makes copies safe to use on other threads — a fresh copy notifies nobody until observers are explicitly added to it. Copy-assignment likewise leaves the target's own watchers untouched.

Member Function Documentation

AddObserver() [1/2]

void bertini::Observable::AddObserver ( AnyObserver & new_observer ) const

inline

Add an observer (non-owning) to observe this observable.

Stores only a raw reference: the caller is responsible for keeping the observer alive while it is attached. This is the right overload for stack-allocated C++ observers added and removed within a scope. For an observer whose lifetime you would rather have tracked, see the shared_ptr overload.

Observers that override SubscribedEventTypes() with a non-empty list are registered in a type-indexed map so NotifyObservers only calls them for events they declared interest in. Observers returning an empty list (the default) are placed in a catch-all list and receive every event.

Safe to call from inside an observer's Observe() (i.e. during a notification): the add is deferred and applied once the current notification loop finishes. This is what lets a "meta-observer" attach new observers in response to events.

Exceptions

IncompatibleObserver

if the observer's ObservedKind() is not one this observable can be observed as.

AddObserver() [2/2]

void bertini::Observable::AddObserver ( std::shared_ptr< AnyObserver > const & new_observer ) const

inline

Add an observer whose lifetime is co-owned by this observable.

The observable keeps a shared_ptr, so the observer stays alive (and keeps receiving events) for as long as it is attached, even after the caller drops their own reference — "attach it and forget it", with no dangling. It is released when RemoveObserver is called or this observable is destroyed. (Stack-allocated C++ observers can't be shared_ptr-owned; use the reference overload for those.)

Exceptions

IncompatibleObserver

if incompatible (see the reference overload).

HasObservers()

bool bertini::Observable::HasObservers ( ) const

inlineprotected

Whether anyone is currently observing (conservative).

Lets an emitter skip constructing an event – and any work needed to build its payload, such as a numeric-type conversion – when there is no observer to receive it. Conservative: returns true if any watcher list is non-empty (even if a stale, emptied typed bucket lingers), so it never wrongly suppresses a real observer.

NotifyObservers() [1/2]

void bertini::Observable::NotifyObservers ( AnyEvent & e ) const

inlineprotected

Notify all observers of a (mutable) event.

NotifyObservers() [2/2]

void bertini::Observable::NotifyObservers ( AnyEvent const & e ) const

inlineprotected

Sends an event to observers that subscribed to its exact dynamic type, then to all catch-all (untyped) observers.

Mutations of the observer lists are deferred for the duration of a notification (see AddObserver/RemoveObserver), so iterating the live lists here is safe even when an observer subscribes/unsubscribes mid-dispatch. An observer that returns ObserveResult::Unsubscribe is dropped once the (possibly nested) notification completes. The depth counter keeps this correct under re-entrant emission.

ObservableIsA()

virtual bool bertini::Observable::ObservableIsA ( std::type_index t ) const

inlinevirtual

Whether this observable may be observed as the given type.

Drives the compatibility check in AddObserver. The default accepts the wildcard typeid(void) and this observable's own dynamic type. An observable that emits its events templated on a base type (so a single observer type serves many concrete observables) should also accept that base type — e.g. ZeroDim accepts AnyZeroDim.

Reimplemented in bertini::algorithm::HomotopySolver< TrackerType, EndgameType, SystemType >, and bertini::algorithm::HomotopySolver< A, B, C >.

operator=()

Observable & bertini::Observable::operator= ( Observable const & )

inline

Copy-assignment: leaves the target's own watcher list untouched (see the copy ctor note).

RemoveObserver()

void bertini::Observable::RemoveObserver ( AnyObserver & observer ) const

inline

Remove an observer from this observable.

Like AddObserver, this is safe to call during a notification: the removal is deferred until the current notification loop finishes.