Observer::Publisher< Message, NotifyAll > Class Template Reference

An object that sends messages to an open-ended list of subscribed callbacks. More...

#include <Observer.h>

Inheritance diagram for Observer::Publisher< Message, NotifyAll >:

Collaboration diagram for Observer::Publisher< Message, NotifyAll >:

Classes
struct	Record

Public Types
using	message_type = Message
using	CallbackReturn = std::conditional_t< NotifyAll, void, bool >
using	Callback = std::function< CallbackReturn(const Message &) >
	Type of functions that can be connected to the Publisher. More...

Public Member Functions
template<typename Alloc = std::allocator<Record>>
	Publisher (ExceptionPolicy *pPolicy=nullptr, Alloc a={})
	Constructor supporting type-erased custom allocation/deletion. More...
	Publisher (Publisher &&)=default
Publisher &	operator= (Publisher &&)=default
Subscription	Subscribe (Callback callback)
	Connect a callback to the Publisher; later-connected are called earlier. More...
template<typename Object , typename Return , typename... Args>
Subscription	Subscribe (Object &obj, Return(Object::*callback)(Args...))
	Overload of Subscribe takes an object and pointer-to-member-function. More...

Static Public Attributes
static constexpr bool	notifies_all = NotifyAll

Protected Member Functions
CallbackReturn	Publish (const Message &message)
	Send a message to connected callbacks. More...

Private Attributes
std::shared_ptr< detail::RecordList >	m_list
std::function< std::shared_ptr< detail::RecordBase >(Callback)>	m_factory

Detailed Description

template<typename Message = Message, bool NotifyAll = true>
class Observer::Publisher< Message, NotifyAll >

An object that sends messages to an open-ended list of subscribed callbacks.

Intended for single-threaded use only. Move-only; allows type-erased custom allocation.

Template Parameters

Message	the type of message
NotifyAll	if true, callback return values are ignored; else, a callback returning true causes earlier subscribed callbacks to be skipped

Definition at line 108 of file Observer.h.

Member Typedef Documentation

Callback

template<typename Message = Message, bool NotifyAll = true>

using Observer::Publisher< Message, NotifyAll >::Callback = std::function< CallbackReturn(const Message&) >

Type of functions that can be connected to the Publisher.

Definition at line 130 of file Observer.h.

CallbackReturn

template<typename Message = Message, bool NotifyAll = true>

using Observer::Publisher< Message, NotifyAll >::CallbackReturn = std::conditional_t<NotifyAll, void, bool>

Definition at line 127 of file Observer.h.

message_type

template<typename Message = Message, bool NotifyAll = true>

using Observer::Publisher< Message, NotifyAll >::message_type = Message

Definition at line 114 of file Observer.h.

Constructor & Destructor Documentation

Publisher() [1/2]

template<typename Message , bool NotifyAll>

template<typename Alloc >

Observer::Publisher< Message, NotifyAll >::Publisher ( ExceptionPolicy *  pPolicy = nullptr, Alloc  a = {}  )

inlineexplicit

Constructor supporting type-erased custom allocation/deletion.

Parameters

pPolicy

if null, exceptions from callbacks are caught and ignored; else, *pPolicy must have a lifetime encompassing the Publisher's

Definition at line 176 of file Observer.h.

: m_list{ std::allocate_shared<detail::RecordList>( a, pPolicy,
    []( // The visitor.  Lambda with no capture converts to pointer-to-function
      const detail::RecordBase &recordBase, const void *arg){
      auto &record = static_cast<const Record&>(recordBase);
      assert(arg);
      auto &message = *static_cast<const Message*>(arg);
      assert(record.callback);
      // Calling foreign code!  Which is why we have an exception policy.
      if constexpr (NotifyAll)
         return (record.callback(message), false);
      else
         return record.callback(message);
   }
) }
, m_factory( [a = move(a)](Callback callback) {
   return std::allocate_shared<Record>(a, move(callback));
} )
{}

Publisher() [2/2]

template<typename Message = Message, bool NotifyAll = true>

Observer::Publisher< Message, NotifyAll >::Publisher ( Publisher< Message, NotifyAll > &&  )

default

Member Function Documentation

operator=()

template<typename Message = Message, bool NotifyAll = true>

Publisher & Observer::Publisher< Message, NotifyAll >::operator= ( Publisher< Message, NotifyAll > &&  )

default

Publish()

template<typename Message , bool NotifyAll>

auto Observer::Publisher< Message, NotifyAll >::Publish ( const Message &  message )

inlineprotected

Send a message to connected callbacks.

Later-connected are called earlier; if !NotifyAll, any callback may return true, to stop the notification; see also class ExceptionPolicy

Returns

if NotifyAll, then void; else, whether the visit was stopped (either because a callback returned true, or the exception policy consumed an exception, and ordered a stop)

Definition at line 207 of file Observer.h.

{
   bool result = m_list->Visit(&message);
   if constexpr (!NotifyAll)
      return result;
}

Referenced by AColor::ApplyUpdatedImages(), PrefsListener::Broadcast(), and DeviceManager::Rescan().

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Subscribe() [1/2]

template<typename Message , bool NotifyAll>

auto Observer::Publisher< Message, NotifyAll >::Subscribe

(

Callback

callback

)

Connect a callback to the Publisher; later-connected are called earlier.

During Publish(), the callback may have the side-effect of adding or removing other Subscriptions. Added subscriptions will not be called, and removed ones, if not called already, will not be called after.

Precondition

callback != nullptr

Definition at line 199 of file Observer.h.

{
   assert(callback); // precondition
   return m_list->Subscribe(m_factory(move(callback)));
}

Referenced by AdornedRulerPanel::AdornedRulerPanel(), DeviceToolBar::DeviceToolBar(), WaveTrackControls::GainSlider(), ViewActions::Handler::Handler(), HistoryDialog::HistoryDialog(), PrefsListener::Impl::Impl(), NewDefaultPlaybackPolicy::Initialize(), EffectUIHost::InitializeRealtime(), LyricsPanel::LyricsPanel(), MenuManager::MenuManager(), MixerBoard::MixerBoard(), AudacityApp::OnInit(), WaveTrackControls::PanSlider(), PlayIndicatorOverlay::PlayIndicatorOverlay(), MixerToolBar::Populate(), ProjectManager::ProjectManager(), ProjectWindow::ProjectWindow(), ScrubbingOverlay::ScrubbingOverlay(), SqliteSampleBlockFactory::SqliteSampleBlockFactory(), ThemedButtonWrapper< ButtonBase >::ThemedButtonWrapper(), ThemedWindowWrapper< WindowBase >::ThemedWindowWrapper(), SelectHandle::TimerHandler::TimerHandler(), TimeToolBar::TimeToolBar(), TrackPanel::TrackPanel(), and anonymous_namespace{TrackView.cpp}::TrackPositioner::TrackPositioner().

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Subscribe() [2/2]

template<typename Message = Message, bool NotifyAll = true>

template<typename Object , typename Return , typename... Args>

Subscription Observer::Publisher< Message, NotifyAll >::Subscribe ( Object &  obj, Return(Object::*)(Args...)  callback  )

inline

Overload of Subscribe takes an object and pointer-to-member-function.

Definition at line 144 of file Observer.h.

   {
      return Subscribe( [&obj, callback](const Message &message){
         return (obj.*callback)(message);
      } );
   }

Member Data Documentation

m_factory

template<typename Message = Message, bool NotifyAll = true>

std::function<std::shared_ptr<detail::RecordBase>(Callback)> Observer::Publisher< Message, NotifyAll >::m_factory

private

Definition at line 171 of file Observer.h.

m_list

template<typename Message = Message, bool NotifyAll = true>

std::shared_ptr<detail::RecordList> Observer::Publisher< Message, NotifyAll >::m_list

private

Definition at line 170 of file Observer.h.

notifies_all

template<typename Message = Message, bool NotifyAll = true>

constexpr bool Observer::Publisher< Message, NotifyAll >::notifies_all = NotifyAll

staticconstexpr

Definition at line 113 of file Observer.h.

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

• Observer.h