D++ (DPP)  10.0.30
C++ Discord API Bot Library
Setting Default Values on Select Menus.

This tutorial will cover how to set the default value for a select menu (that isn't a text select menu)!

Note
This only works for the following types of select menus: user, role, mentionable, and channel. The default type of a select menu (as shown in this page) does not work for this, as that supports a "placeholder".
#include <dpp/dpp.h>
int main() {
dpp::cluster bot("token");
/* The event is fired when someone issues your commands */
bot.on_slashcommand([&bot](const dpp::slashcommand_t& event) {
/* Check which command they ran */
if (event.command.get_command_name() == "select") {
/* Create a message */
dpp::message msg(event.command.channel_id, "This text has a select menu!");
/* Add an action row, and a select menu within the action row.
*
* Your default values are limited to max_values,
* meaning you can't add more default values than the allowed max values.
*/
msg.add_component(
dpp::component().add_component(
dpp::component()
.set_type(dpp::cot_role_selectmenu)
.set_min_values(2)
.set_max_values(2)
.add_default_value(dpp::snowflake{667756886443163648}, dpp::cdt_role)
.set_id("myselectid")
)
);
/* Reply to the user with our message. */
event.reply(msg);
}
});
bot.on_ready([&bot](const dpp::ready_t& event) {
if (dpp::run_once<struct register_bot_commands>()) {
/* Create and register a command when the bot is ready */
bot.global_command_create(dpp::slashcommand("select", "Select something at random!", bot.me.id));
}
});
bot.start(dpp::st_wait);
return 0;
}

If all went well, you should have something like this!

unicode_emoji.h
dpp::slashcommand_t
User has issued a slash command.
Definition: dispatcher.h:715
dpp.h
dpp::st_wait
@ st_wait
Wait forever on a condition variable.
Definition: cluster.h:101
dpp::cdt_role
@ cdt_role
Definition: message.h:220
main
int main()
Definition: soak.cpp:28
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::slashcommand
Represents an application command, created by your bot either globally, or on a guild.
Definition: appcommand.h:1358
dpp::interaction::get_command_name
std::string get_command_name() const
Get the command name for a command interaction.
Definition: slashcommand.cpp:487
dpp::cluster
The cluster class represents a group of shards and a command queue for sending and receiving commands...
Definition: cluster.h:99
dpp::ready_t
Session ready.
Definition: dispatcher.h:981