Attaching a File to a Message

To attach a local file to an message, you can use dpp::utility::read_file. It's a helper function from D++ that allows you to read the file's content and sent it to discord.

An example of this:

#include <dpp/dpp.h>
 
int main() {
    dpp::cluster bot("token");
 
    bot.on_log(dpp::utility::cout_logger());
 
    /* 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() == "file") {
            dpp::message msg(event.command.channel_id, "Hey there, I've got a new file!");
 
            /* attach the file to the message */
            msg.add_file("foobar.txt", dpp::utility::read_file("path_to_your_file.txt"));
 
            /* Reply to the user with the message, with our file attached. */
            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("file", "Send a message with a file attached!", bot.me.id));
        }
    });
 
    bot.start(dpp::st_wait);
 
    return 0;
}

Attachments via URL aren't possible. But there's a workaround for this! You can download the file and then attach it to the message.

Amazingly, D++ also has a function for this! You can use dpp::cluster::request to make HTTP requests, allowing you to go ahead and pull the content from a URL.

The following example program shows how to request a file and attach it to a message:

#include <dpp/dpp.h>
 
int main() {
    dpp::cluster bot("token");
 
    bot.on_log(dpp::utility::cout_logger());
 
    /* 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() == "file") {
 
            /* Request the image from the URL specified and capture the event in a lambda. */
            bot.request("https://dpp.dev/DPP-Logo.png", dpp::m_get, [event](const dpp::http_request_completion_t & httpRequestCompletion) {
 
                /* Create a message */
                dpp::message msg(event.command.channel_id, "This is my new attachment:");
 
                /* Attach the image to the message, only on success (Code 200). */
                if (httpRequestCompletion.status == 200) {
                    msg.add_file("logo.png", httpRequestCompletion.body);
                }
 
                /* Send the message, with our attachment. */
                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("file", "Send a message with an image attached from the internet!", bot.me.id));
        }
    });
 
    bot.start(dpp::st_wait);
 
    return 0;
}

Here's another example of how to add a local image to an embed.

Upload the image in the same message as the embed and then reference it in the embed.

#include <dpp/dpp.h>
 
int main() {
    dpp::cluster bot("token");
 
    bot.on_log(dpp::utility::cout_logger());
 
    /* 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() == "file") {
            /* Create a message. */
            dpp::message msg(event.command.channel_id, "");
 
            /* Attach the image to the message we just created. */
            msg.add_file("image.jpg", dpp::utility::read_file("path_to_your_image.jpg"));
 
            /* Create an embed. */
            dpp::embed embed;
            embed.set_image("attachment://image.jpg"); /* Set the image of the embed to the attached image. */
 
            /* Add the embed to the message. */
            msg.add_embed(embed);
 
            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("file", "Send a local image along with an embed with the image!", bot.me.id));
        }
    });
 
    bot.start(dpp::st_wait);
 
    return 0;
}