Collecting Reactions

D++ comes with many useful helper classes, but amongst these is something called dpp::collector. Collector is a template which can be specialised to automatically collect objects of a predetermined type from events for a specific interval of time. Once this time period is up, or the class is otherwise signalled, a method is called with the complete set of collected objects.

In the example below, we will use it to collect all reactions on a message.

#include <dpp/dpp.h>
 
/* To create a collector we must derive from dpp::collector. As dpp::collector is a complicated template,
 * various pre-made forms exist such as this one, reaction_collector.
 */
class react_collector : public dpp::reaction_collector {
public:
    /* Collector will run for 20 seconds */
    react_collector(dpp::cluster* cl, dpp::snowflake id) : dpp::reaction_collector(cl, 20, id) { }
 
    /* Override the "completed" event and then output the number of collected reactions as a message. */
    virtual void completed(const std::vector<dpp::collected_reaction>& list) override {
        if (list.size()) {
            owner->message_create(dpp::message(list[0].react_channel->id, "I collected " + std::to_string(list.size()) + " reactions!"));
        } else {
            owner->message_create(dpp::message("... I got nothin'."));
        }
    }
};
 
 
int main() {
    /* Create bot */
    dpp::cluster bot("token", dpp::i_default_intents | dpp::i_message_content);
 
    /* Pointer to reaction collector */
    react_collector* r = nullptr;
 
    bot.on_log(dpp::utility::cout_logger());
 
    /* Message handler */
    bot.on_message_create([&r, &bot](const dpp::message_create_t& event) {
 
        /* If someone sends a message that has the text 'collect reactions!' start a reaction collector */
        if (event.msg.content == "collect reactions!" && r == nullptr) {
            /* Create a new reaction collector to collect reactions */
            r = new react_collector(&bot, event.msg.id);
        }
 
    });
 
    /* Start bot */
    bot.start(dpp::st_wait);
 
    return 0;
}