D++ (DPP)  10.0.30
C++ Discord API Bot Library
Making simple commands

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.

Several steps in one

Note
The next example assumes you are already familiar with how to use slash commands, parameters, and sending files through a command.

With coroutines, it becomes a lot easier to do several asynchronous requests for one task. As an example an "addemoji" command taking a file and a name as a parameter. This means downloading the emoji, submitting it to Discord, and finally replying, with some error handling along the way. Normally we would have to use callbacks and some sort of object keeping track of our state, but with coroutines, the function can simply pause and be resumed when we receive the response to our request :

#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() == "addemoji") {
dpp::cluster *cluster = event.from->creator;
// Retrieve parameter values
dpp::snowflake file_id = std::get<dpp::snowflake>(event.get_parameter("file"));
std::string emoji_name = std::get<std::string>(event.get_parameter("name"));
// Get the attachment from the resolved list
const dpp::attachment &attachment = event.command.get_resolved_attachment(file_id);
// For simplicity for this example we only support PNG
if (attachment.content_type != "image/png") {
// While we could use event.co_reply, we can just use event.reply, as we will exit the command anyway and don't need to wait on the result
event.reply("Error: type " + attachment.content_type + " not supported");
co_return;
}
// Send a "<bot> is thinking..." message, to wait on later so we can edit
// Download and co_await the result
dpp::http_request_completion_t response = co_await cluster->co_request(attachment.url, dpp::m_get);
if (response.status != 200) { // Page didn't send the image
co_await thinking; // Wait for the thinking response to arrive so we can edit
event.edit_response("Error: could not download the attachment");
} else {
// Load the image data in a dpp::emoji
dpp::emoji emoji(emoji_name);
emoji.load_image(response.body, dpp::image_type::i_png);
// Create the emoji and co_await the response
dpp::confirmation_callback_t confirmation = co_await cluster->co_guild_emoji_create(event.command.guild_id, emoji);
co_await thinking; // Wait for the thinking response to arrive so we can edit
if (confirmation.is_error()) {
event.edit_response("Error: could not add emoji: " + confirmation.get_error().message);
} else { // Success
event.edit_response("Successfully added " + confirmation.get<dpp::emoji>().get_mention()); // Show the new emoji
}
}
}
});
bot.on_ready([&bot](const dpp::ready_t& event) {
if (dpp::run_once<struct register_bot_commands>()) {
dpp::slashcommand command("addemoji", "Add an emoji", bot.me.id);
// Add file and name as required parameters
command.add_option(dpp::command_option(dpp::co_attachment, "file", "Select an image", true));
command.add_option(dpp::command_option(dpp::co_string, "name", "Name of the emoji to add", true));
bot.global_command_create(command);
}
});
bot.start(dpp::st_wait);
return 0;
}

I heard you liked tasks

Note
This next example is fairly advanced and makes use of many of both C++ and D++'s advanced features.

Earlier we mentioned two other types of coroutines provided by dpp: dpp::coroutine and dpp::task. They both take their return type as a template parameter, which may be void. Both dpp::job and dpp::task start on the constructor for asynchronous execution, however only the latter can be co_await-ed, this allows you to retrieve its return value. If a dpp::task is destroyed before it ends, it is cancelled and will stop when it is resumed from the next co_await. dpp::coroutine also has a return value and can be co_await-ed, however it only starts when co_await-ing, meaning it is executed synchronously.

Here is an example of a command making use of dpp::task to retrieve the avatar of a specified user, or if missing, the sender:

#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() == "avatar") {
// Make a nested coroutine to fetch the guild member requested, that returns it as an optional
constexpr auto resolve_member = [](const dpp::slashcommand_t &event) -> dpp::task<std::optional<dpp::guild_member>> {
const dpp::command_value &user_param = event.get_parameter("user");
dpp::snowflake user_id;
if (std::holds_alternative<std::monostate>(user_param)) {
user_id = event.command.usr.id; // Parameter is empty so user is sender
}
else if (std::holds_alternative<dpp::snowflake>(user_param)) {
user_id = std::get<dpp::snowflake>(user_param); // Parameter has a user
}
// If we have the guild member in the command's resolved data, return it
const auto &member_map = event.command.resolved.members;
if (auto member = member_map.find(user_id); member != member_map.end()) {
co_return member->second;
}
// Try looking in guild cache
dpp::guild *guild = dpp::find_guild(event.command.guild_id);
if (guild) {
// Look in guild's member cache
if (auto member = guild->members.find(user_id); member != guild->members.end()) {
co_return member->second;
}
}
// Finally if everything else failed, request API
dpp::confirmation_callback_t confirmation = co_await event.from->creator->co_guild_get_member(event.command.guild_id, user_id);
if (confirmation.is_error()) {
co_return std::nullopt; // Member not found, return empty
} else {
co_return confirmation.get<dpp::guild_member>();
}
};
// Send a "<bot> is thinking..." message, to wait on later so we can edit
// Call our coroutine defined above to retrieve the member requested
std::optional<dpp::guild_member> member = co_await resolve_member(event);
if (!member.has_value()) {
// Wait for the thinking response to arrive to make sure we can edit
co_await thinking;
event.edit_original_response(dpp::message{"User not found in this server!"});
co_return;
}
std::string avatar_url = member->get_avatar_url(512);
if (avatar_url.empty()) { // Member does not have a custom avatar for this server, get their user avatar
dpp::confirmation_callback_t confirmation = co_await event.from->creator->co_user_get_cached(member->user_id);
if (confirmation.is_error()) {
// Wait for the thinking response to arrive to make sure we can edit
co_await thinking;
event.edit_original_response(dpp::message{"User not found!"});
co_return;
}
avatar_url = confirmation.get<dpp::user_identified>().get_avatar_url(512);
}
// Wait for the thinking response to arrive to make sure we can edit
co_await thinking;
event.edit_original_response(dpp::message{avatar_url});
}
});
bot.on_ready([&bot](const dpp::ready_t& event) {
if (dpp::run_once<struct register_bot_commands>()) {
dpp::slashcommand command("avatar", "Get your or another user's avatar image", bot.me.id);
command.add_option(dpp::command_option(dpp::co_user, "user", "User to fetch the avatar from"));
bot.global_command_create(command);
}
});
bot.start(dpp::st_wait);
return 0;
}
dpp::co_attachment
@ co_attachment
File attachment type.
Definition: appcommand.h:123
dpp::confirmation_callback_t::get
T get() const
Get the stored value via std::get.
Definition: restresults.h:342
dpp::slashcommand_t
User has issued a slash command.
Definition: dispatcher.h:715
if
if(!file_exists(getenv("HOME") . "/dpp-web"))
Definition: makedocs.php:4
dpp.h
dpp::st_wait
@ st_wait
Wait forever on a condition variable.
Definition: cluster.h:101
dpp::user_identified
A user with additional fields only available via the oauth2 identify scope.
Definition: user.h:482
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::m_get
@ m_get
GET.
Definition: queues.h:205
main
int main()
Definition: soak.cpp:28
dpp::confirmation_callback_t::is_error
bool is_error() const
Returns true if the call resulted in an error rather than a legitimate value in the confirmation_call...
Definition: confirmation.cpp:66
dpp::message
Represents messages sent and received on Discord.
Definition: message.h:2007
dpp::http_request_completion_t
The result of any HTTP request.
Definition: queues.h:130
dpp::interaction_create_t::command
interaction command
command interaction
Definition: dispatcher.h:698
dpp::utility::cout_logger
std::function< void(const dpp::log_t &)> DPP_EXPORT cout_logger()
Get a default logger that outputs to std::cout.
Definition: dispatcher.h:228
dpp::async
A co_await-able object handling an API call in parallel with the caller.
Definition: async.h:403
dpp::co_user
@ co_user
A user snowflake id.
Definition: appcommand.h:98
dpp::slashcommand
Represents an application command, created by your bot either globally, or on a guild.
Definition: appcommand.h:1358
dpp::co_string
@ co_string
A string value.
Definition: appcommand.h:83
dpp::interaction::get_command_name
std::string get_command_name() const
Get the command name for a command interaction.
Definition: slashcommand.cpp:487
dpp::command_option
Each command option is a command line parameter.
Definition: appcommand.h:222
dpp::unicode_emoji::thinking
constexpr const char thinking[]
Definition: unicode_emoji.h:1691
dpp::cluster
The cluster class represents a group of shards and a command queue for sending and receiving commands...
Definition: cluster.h:99
dpp::interaction_create_t::co_thinking
dpp::async< dpp::confirmation_callback_t > co_thinking(bool ephemeral=false) const
Set the bot to 'thinking' state where you have up to 15 minutes to respond.
Definition: dispatcher.cpp:244
dpp::confirmation_callback_t
The results of a REST call wrapped in a convenient struct.
Definition: restresults.h:274
dpp::cluster::on_log
event_router_t< log_t > on_log
Called when a log message is to be written to the log.
Definition: cluster.h:481
dpp::ready_t
Session ready.
Definition: dispatcher.h:981