concurrent::AsyncEventSource< Args > Class Template Reference

#include <userver/concurrent/async_event_source.hpp>

Detailed Description

template<typename... Args>
class concurrent::AsyncEventSource< Args >

The read-only side of an event channel. Events are delivered to listeners in a strict FIFO order, i.e. only after the event was processed a new event may appear for processing, same listener is never called concurrently.

Definition at line 100 of file async_event_source.hpp.

Inheritance diagram for concurrent::AsyncEventSource< Args >:

Public Types
using	Function = std::function<void(Args... args)>

Public Member Functions
template<class Class >
AsyncEventSubscriberScope	AddListener (Class *obj, std::string_view name, void(Class::*func)(Args...))
	Subscribes to updates from this event source.
AsyncEventSubscriberScope	AddListener (FunctionId id, std::string_view name, Function &&func)
	A type-erased version of AddListener.
void	RemoveListener (FunctionId, UnsubscribingKind) noexcept override=0
	Used by AsyncEventSubscriberScope to cancel an event subscription.

Protected Member Functions
virtual AsyncEventSubscriberScope	DoAddListener (FunctionId id, std::string_view name, Function &&func)=0

Member Typedef Documentation

Function

template<typename... Args>

using concurrent::AsyncEventSource< Args >::Function = std::function<void(Args... args)>

Definition at line 102 of file async_event_source.hpp.

Member Function Documentation

AddListener() [1/2]

template<typename... Args>

template<class Class >

AsyncEventSubscriberScope concurrent::AsyncEventSource< Args >::AddListener ( Class * obj, std::string_view name, void(Class::*)(Args...) func )

inline

Subscribes to updates from this event source.

The listener won't be called immediately. To process the current value and then listen to updates, use UpdateAndListen of specific event channels.

Warning

Listeners should not be added or removed while processing the event inside another listener.

Example usage:

UTEST(AsyncEventChannel, AddListenerSample) {
    WeatherStorage weather_storage(WeatherKind::kSunny);
    std::vector<WeatherKind> recorded_weather;
 
    concurrent::AsyncEventSubscriberScope recorder = weather_storage.GetSource().AddListener(
        concurrent::FunctionId(&recorder), "recorder", [&](WeatherKind weather) { recorded_weather.push_back(weather); }
    );
 
    weather_storage.Set(WeatherKind::kRainy);
    weather_storage.Set(WeatherKind::kSunny);
    weather_storage.Set(WeatherKind::kSunny);
    EXPECT_EQ(recorded_weather, (std::vector{WeatherKind::kRainy, WeatherKind::kSunny, WeatherKind::kSunny}));
 
    recorder.Unsubscribe();
}

Parameters

obj	the subscriber, which is the owner of the listener method, and is also used as the unique identifier of the subscription for this AsyncEventSource
name	the name of the subscriber, for diagnostic purposes
func	the listener method, usually called On<DataName>Update, e.g. OnConfigUpdate or OnCacheUpdate

Returns

a AsyncEventSubscriberScope controlling the subscription, which should be stored as a member in the subscriber; Unsubscribe should be called explicitly

Definition at line 127 of file async_event_source.hpp.

AddListener() [2/2]

template<typename... Args>

AsyncEventSubscriberScope concurrent::AsyncEventSource< Args >::AddListener ( FunctionId id, std::string_view name, Function && func )

inline

A type-erased version of AddListener.

Parameters

id	the unique identifier of the subscription
name	the name of the subscriber, for diagnostic purposes
func	the callback used for event notifications

Definition at line 136 of file async_event_source.hpp.

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

• userver/concurrent/async_event_source.hpp