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concurrent::AsyncEventSource< Args > Class Template Referenceabstract

The read-only side of an event channel. Events are delivered to listeners in a strict FIFO order. More...

#include <userver/concurrent/async_event_source.hpp>

+ Inheritance diagram for concurrent::AsyncEventSource< Args >:
+ Collaboration 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

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.

Definition at line 98 of file async_event_source.hpp.

Member Typedef Documentation

◆ Function

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

Definition at line 100 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 

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.

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::FunctionId(&recorder), "recorder",
[&](WeatherKind weather) { recorded_weather.push_back(weather); });
(std::vector{WeatherKind::kRainy, WeatherKind::kSunny,
objthe subscriber, which is the owner of the listener method, and is also used as the unique identifier of the subscription for this AsyncEventSource
namethe name of the subscriber, for diagnostic purposes
functhe listener method, usually called On<DataName>Update, e.g. OnConfigUpdate or OnCacheUpdate
a AsyncEventSubscriberScope controlling the subscription, which should be stored as a member in the subscriber; Unsubscribe should be called explicitly

Definition at line 125 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 

A type-erased version of AddListener.

idthe unique identifier of the subscription
namethe name of the subscriber, for diagnostic purposes
functhe callback used for event notifications

Definition at line 136 of file async_event_source.hpp.

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