D++ (DPP)
C++ Discord API Bot Library
Waiting for events

Warning
D++ Coroutines are a very new feature and are currently only supported by D++ on g++ 11, clang/LLVM 14, and MSVC 19.37 or above. Additionally, D++ must be built with the CMake option DPP_CORO, and your program must both define the macro DPP_CORO and use C++20 or above. The feature is experimental and may have bugs or even crashes, please report any to GitHub Issues or to our Discord Server.

D++ makes it possible to await events: simple use co_await on any of the event routers, such as on_message_create, and your coroutine will be suspended until the next event fired by this event router. You can also co_await the return of an event router's when() method while passing it a predicate function object, it will only resume your coroutine when the predicate returns true. Be aware that your coroutine is attached to the event router only when you call co_await and not before, and will be detached as it is resumed.

Note
When the event router resumes your coroutine, it will give you a reference to the event object. This will likely mean it will be destroyed after your next co_await, make sure to save it in a local variable if you need it for longer.
#include <dpp/dpp.h>
int main() {
dpp::cluster bot{"token"};
bot.on_slashcommand([](const dpp::slashcommand_t& event) -> dpp::task<void> {
if (event.command.get_command_name() == "test") {
// Make a message and add a button with its custom ID set to the command interaction's ID so we can identify it
dpp::message m{"Test"};
std::string id{event.command.id.str()};
m.add_component(
.set_label("Click me!")
.set_id(id)
)
);
co_await event.co_reply(m);
dpp::button_click_t click_event = co_await event.from->creator->on_button_click.when(
// Note!! Due to a bug in g++11 and g++12, id must be captured as a reference here or the compiler will destroy it twice. This is fixed in g++13
[&id] (dpp::button_click_t const &b) {
return b.custom_id == id;
}
);
// Acknowledge the click and edit the original response, removing the button
click_event.reply();
event.edit_original_response(dpp::message{"You clicked the button!"});
}
});
bot.on_ready([&bot](const dpp::ready_t& event) {
if (dpp::run_once<struct register_bot_commands>()) {
dpp::slashcommand command{"test", "Test awaiting for an event", bot.me.id};
bot.global_command_create(command);
}
});
bot.start(dpp::st_wait);
return 0;
}

Note that there is a problem with that! If the user never clicks your button, or if the message gets deleted, your coroutine will be stuck waiting... And waiting... Forever until your bot shuts down, occupying a space in memory. This is where the next example comes into play as a solution, with a button that expires with time.

dpp::cluster::on_button_click
event_router_t< button_click_t > on_button_click
Called when a button is clicked attached to a message. Button clicks are triggered by discord when bu...
Definition: cluster.h:525
dpp::managed::id
snowflake id
Unique ID of object set by Discord. This value contains a timestamp, worker ID, internal server ID,...
Definition: managed.h:79
dpp::interaction_create_t::co_reply
dpp::async< dpp::confirmation_callback_t > co_reply() const
Acknowledge interaction without displaying a message to the user, for use with button and select menu...
dpp::slashcommand_t
User has issued a slash command.
Definition: dispatcher.h:715
dpp::interaction_create_t::edit_original_response
void edit_original_response(const message &m, command_completion_event_t callback=utility::log_error()) const
Edit original response message for this interaction.
dpp::st_wait
@ st_wait
Wait forever on a condition variable. The cluster will spawn threads for each shard and start() will ...
Definition: cluster.h:101
dpp::discord_client::creator
class dpp::cluster * creator
Owning cluster.
Definition: discordclient.h:275
dpp::task
A coroutine task. It starts immediately on construction and can be co_await-ed, making it perfect for...
Definition: coro/coro.h:166
dpp::component::set_id
component & set_id(const std::string &id)
Set the id of the component. For action rows, this field is ignored. Setting the id will auto-set the...
dpp::message
Represents messages sent and received on Discord.
Definition: message.h:1772
dpp::event_dispatch_t::from
discord_client * from
Shard the event came from. Note that for some events, notably voice events, this may be nullptr.
Definition: dispatcher.h:110
dpp::interaction_create_t::command
interaction command
command interaction
Definition: dispatcher.h:698
dpp::component::set_type
component & set_type(component_type ct)
Set the type of the component. Button components (type dpp::cot_button) should always be contained wi...
dpp::slashcommand
Represents an application command, created by your bot either globally, or on a guild.
Definition: appcommand.h:1358
dpp::utility::cout_logger
std::function< void(const dpp::log_t &)> DPP_EXPORT cout_logger()
Get a default logger that outputs to std::cout. e.g.
Definition: dispatcher.h:228
dpp::interaction::get_command_name
std::string get_command_name() const
Get the command name for a command interaction.
dpp::cot_button
@ cot_button
Clickable button.
Definition: message.h:86
dpp::component
Represents the component object. A component is a clickable button or drop down list within a discord...
Definition: message.h:353
dpp::component::add_component
component & add_component(const component &c)
Add a sub-component, only valid for action rows. Adding subcomponents to a component will automatical...
dpp::cluster
The cluster class represents a group of shards and a command queue for sending and receiving commands...
Definition: cluster.h:99
dpp::button_click_t
Click on button.
Definition: dispatcher.h:723
dpp::unicode_emoji::m
constexpr const char m[]
Definition: unicode_emoji.h:5304
dpp::component::set_label
component & set_label(const std::string &label)
Set the label of the component, e.g. button text. For action rows, this field is ignored....
dpp::cluster::on_log
event_router_t< log_t > on_log
Called when a log message is to be written to the log. You can attach any logging system here you wis...
Definition: cluster.h:481
dpp::ready_t
Session ready.
Definition: dispatcher.h:981
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