dpp::event_router_t< T > Class Template Reference

Handles routing of an event to multiple listeners. Multiple listeners may attach to the event_router_t by means of operator(). Passing a lambda into operator() attaches to the event. More...

#include <event_router.h>

Public Member Functions
	event_router_t ()=default
	Construct a new event_router_t object. More...
	~event_router_t ()
	Destructor. Will cancel any coroutine awaiting on events. More...
void	call (const T &event) const
	Call all attached listeners. Listeners may cancel, by calling the event.cancel method. More...
void	call (T &&event) const
	Call all attached listeners. Listeners may cancel, by calling the event.cancel method. More...
template<typename Predicate >
auto	when (Predicate &&pred)
	Obtain an awaitable object that refers to an event with a certain condition. It can be co_await-ed to wait for the next event that satisfies this condition. On resumption the awaiter will be given a reference to the event, saving it in a variable is recommended to avoid variable lifetime issues. More...
auto	operator co_await () noexcept
	Obtain an awaitable object that refers to any event. It can be co_await-ed to wait for the next event. More...
bool	empty () const
	Returns true if the container of listeners is empty, i.e. there is nothing listening for this event right now. More...
	operator bool () const
	Returns true if any listeners are attached. More...
template<typename F >
event_handle	operator() (F &&fun)
	Attach a callable to the event, adding a listener. The callable should either be of the form void(const T&) or dpp::task<void>(const T&) (the latter requires DPP_CORO to be defined), where T is the event type for this event router. More...
template<typename F >
event_handle	attach (F &&fun)
	Attach a callable to the event, adding a listener. The callable should either be of the form void(const T&) or dpp::task<void>(const T&) (the latter requires DPP_CORO to be defined), where T is the event type for this event router. More...
bool	detach (const event_handle &handle)
	Detach a listener from the event using a previously obtained ID. More...

Protected Member Functions
void	set_warning_callback (std::function< void(const T &)> warning_function)
	Next handle to be given out by the event router. More...
void	handle (const T &event) const
	Handle an event. This function should only be used without coro enabled, otherwise use handle_coro. More...
dpp::job	handle_coro (T event) const
	Handle an event as a coroutine, ensuring the lifetime of the event object. More...
void	attach_awaiter (detail::event_router::awaitable< T > *awaiter)
	Attach a suspended coroutine to this event router via detail::event_router::awaitable. It will be resumed and detached when an event satisfying its condition completes, or it is cancelled. More...
void	detach_coro (void *handle)
	Detach an awaiting coroutine handle from this event router. This is mostly called when a detail::event_router::awaitable is cancelled. More...
void	resume_awaiters (const T &event) const
	Resume any awaiter whose predicate matches this event, or is null. More...

Friends
class	cluster
class	detail::event_router::awaitable< T >

Detailed Description

template<class T>
class dpp::event_router_t< T >

Handles routing of an event to multiple listeners. Multiple listeners may attach to the event_router_t by means of operator(). Passing a lambda into operator() attaches to the event.

Dispatchers of the event may call the call() method to cause all listeners to receive the event.

The empty() method will return true if there are no listeners attached to the event_router_t (this can be used to save time by not constructing objects that nobody will ever see).

The detach() method removes an existing listener from the event, using the event_handle ID returned by operator().

This class is used by the library to route all websocket events to listening code.

Example:

// Declare an event that takes log_t as its parameter
event_router_t<log_t> my_event;
 
// Attach a listener to the event
event_handle id = my_event([&](const log_t& cc) {
  std::cout << cc.message << "\n";
});
 
// Construct a log_t and call the event (listeners will receive the log_t object)
log_t lt;
lt.message = "foo";
my_event.call(lt);
 
// Detach from an event using the handle returned by operator()
my_event.detach(id);

Template Parameters

T	type of single parameter passed to event lambda derived from event_dispatch_t

Constructor & Destructor Documentation

event_router_t()

template<class T >

dpp::event_router_t< T >::event_router_t ( )

default

Construct a new event_router_t object.

~event_router_t()

template<class T >

dpp::event_router_t< T >::~event_router_t ( )

inline

Destructor. Will cancel any coroutine awaiting on events.

Exceptions

!	Cancelling a coroutine will throw a dpp::task_cancelled_exception to it. This will be caught in this destructor, however, make sure no other exceptions are thrown in the coroutine after that or it will terminate.

Member Function Documentation

attach()

template<class T >

template<typename F >

event_handle dpp::event_router_t< T >::attach

(

F &&

fun

)

Attach a callable to the event, adding a listener. The callable should either be of the form void(const T&) or dpp::task<void>(const T&) (the latter requires DPP_CORO to be defined), where T is the event type for this event router.

Parameters

fun	Callable to attach to event

Returns

event_handle An event handle unique to this event, used to detach the listener from the event later if necessary.

attach_awaiter()

template<class T >

void dpp::event_router_t< T >::attach_awaiter ( detail::event_router::awaitable< T > *  awaiter )

inlineprotected

Attach a suspended coroutine to this event router via detail::event_router::awaitable. It will be resumed and detached when an event satisfying its condition completes, or it is cancelled.

This is for internal usage only, the user way to do this is to co_await it (which will call this when suspending) This guarantees that the coroutine is indeed suspended and thus can be resumed at any time

Parameters

awaiter

Awaiter to attach

call() [1/2]

template<class T >

void dpp::event_router_t< T >::call ( const T &  event ) const

inline

Call all attached listeners. Listeners may cancel, by calling the event.cancel method.

Parameters

event

Class to pass as parameter to all listeners.

call() [2/2]

template<class T >

void dpp::event_router_t< T >::call ( T &&  event ) const

inline

Call all attached listeners. Listeners may cancel, by calling the event.cancel method.

Parameters

event

Class to pass as parameter to all listeners.

detach()

template<class T >

bool dpp::event_router_t< T >::detach ( const event_handle &  handle )

inline

Detach a listener from the event using a previously obtained ID.

Warning

You cannot call this within an event handler.

Parameters

handle

An ID obtained from operator()

Return values

true	The event was successfully detached
false	The ID is invalid (possibly already detached, or does not exist)

detach_coro()

template<class T >

void dpp::event_router_t< T >::detach_coro ( void *  handle )

inlineprotected

Detach an awaiting coroutine handle from this event router. This is mostly called when a detail::event_router::awaitable is cancelled.

Parameters

handle

Coroutine handle to find in the attached coroutines

empty()

template<class T >

bool dpp::event_router_t< T >::empty ( ) const

inline

Returns true if the container of listeners is empty, i.e. there is nothing listening for this event right now.

Return values

true	if there are no listeners
false	if there are some listeners

handle()

template<class T >

void dpp::event_router_t< T >::handle ( const T &  event ) const

inlineprotected

Handle an event. This function should only be used without coro enabled, otherwise use handle_coro.

handle_coro()

template<class T >

dpp::job dpp::event_router_t< T >::handle_coro ( T  event ) const

inlineprotected

Handle an event as a coroutine, ensuring the lifetime of the event object.

operator bool()

template<class T >

dpp::event_router_t< T >::operator bool ( ) const

inline

Returns true if any listeners are attached.

This is the boolean opposite of event_router_t::empty().

Return values

true	if listeners are attached
false	if no listeners are attached

operator co_await()

template<class T >

auto dpp::event_router_t< T >::operator co_await ( )

inlinenoexcept

Obtain an awaitable object that refers to any event. It can be co_await-ed to wait for the next event.

Example:

dpp::task<> my_handler(const dpp::slashcommand_t& event) {
 co_await event.co_reply(dpp::message().add_component(dpp::component().add_component().set_label("click me!").set_id("test")));
 
 dpp::button_click_t b = co_await c->on_message_create;
 
 // do something on button click
}

This can be combined with dpp::when_any and other awaitables, for example dpp::cluster::co_sleep to create expiring buttons.

Warning

On resumption the awaiter will be given a reference to the event. This means that variable may become dangling at the next co_await, be careful and save it in a variable if you need to.

Returns

awaitable An awaitable object that can be co_await-ed to await an event matching the condition.

operator()()

template<class T >

template<typename F >

event_handle dpp::event_router_t< T >::operator()

(

F &&

fun

)

Attach a callable to the event, adding a listener. The callable should either be of the form void(const T&) or dpp::task<void>(const T&) (the latter requires DPP_CORO to be defined), where T is the event type for this event router.

This has the exact same behavior as using attach.

See also

attach

Parameters

fun	Callable to attach to event

Returns

event_handle An event handle unique to this event, used to detach the listener from the event later if necessary.

resume_awaiters()

template<class T >

void dpp::event_router_t< T >::resume_awaiters ( const T &  event ) const

inlineprotected

Resume any awaiter whose predicate matches this event, or is null.

Parameters

event

Event to compare and pass to accepting awaiters

If state == none (was never awaited), do nothing If state == waiting, prevent resumption, resume on our end If state == resuming || cancelling, ignore

Technically only cancelling || waiting should be possible here We do this by trying to exchange "waiting" with "resuming". If that returns false, this is presumed to be "cancelling"

set_warning_callback()

template<class T >

void dpp::event_router_t< T >::set_warning_callback ( std::function< void(const T &)>  warning_function )

inlineprotected

Next handle to be given out by the event router.

Set the warning callback object used to check that this event is capable of running properly

Parameters

warning_function

A checking function to call

when()

template<class T >

template<typename Predicate >

auto dpp::event_router_t< T >::when ( Predicate &&  pred )

inline

Obtain an awaitable object that refers to an event with a certain condition. It can be co_await-ed to wait for the next event that satisfies this condition. On resumption the awaiter will be given a reference to the event, saving it in a variable is recommended to avoid variable lifetime issues.

Example:

dpp::task<> my_handler(const dpp::slashcommand_t& event) {
 co_await event.co_reply(dpp::message().add_component(dpp::component().add_component().set_label("click me!").set_id("test")));
 
 dpp::button_click_t b = co_await c->on_button_click.with([](const dpp::button_click_t &event){ return event.custom_id == "test"; });
 
 // do something on button click
}

This can be combined with dpp::when_any and other awaitables, for example dpp::cluster::co_sleep to create expiring buttons.

Warning

On resumption the awaiter will be given a reference to the event. This means that variable may become dangling at the next co_await, be careful and save it in a variable if you need to.

Parameters

pred	Predicate to check the event against. This should be a callable of the form bool(const T&) where T is the event type, returning true if the event is to match.

Returns

awaitable An awaitable object that can be co_await-ed to await an event matching the condition.

Friends And Related Function Documentation

cluster

template<class T >

friend class cluster

friend

detail::event_router::awaitable< T >

template<class T >

friend class detail::event_router::awaitable< T >

friend