Tutorial – Building an R Bot in 3 steps

Introduction

In order to build a bot that is continuously running and is able to respond to multiple input data formats, the telegram.bot package features several R6 classes, but the two most important ones here are Updater and Dispatcher.

The Updater class continuously fetches new updates from Telegram and passes them on to the Dispatcher class. If you create an Updater object, it will create a Dispatcher. You can then register handlers of different types in the Dispatcher, which will sort the updates fetched by the Updater according to the handlers you registered, and deliver them to a callback function that you defined. Every handler is an instance of any subclass of the Handler class.

To begin, you’ll need an Access Token. If you already read and followed Introduction to the API, you can use the one you generated then. If not: To generate an Access Token, you have to talk to @BotFather and follow a few simple steps (described here). You should really read the introduction first, though.

With that said, let’s get started!

1. Creating the Updater object

First, you first must create an Updater object. Replace TOKEN with your Telegram Bot’s API Access Token, which looks something like 123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11.

library(telegram.bot)

updater <- Updater(token = "TOKEN")

Recommendation: Following Hadley’s API guidelines it’s unsafe to type the TOKEN just in the R script. It’s better to use environment variables set in .Renviron file.

So let’s say you have named your bot RTelegramBot (it’s the first question you answered to the BotFather when creating it); you can open the .Renviron file with the R commands:

file.edit(path.expand(file.path("~", ".Renviron")))

And put the following line with your TOKEN in your .Renviron:

R_TELEGRAM_BOT_RTelegramBot=TOKEN

If you follow the suggested R_TELEGRAM_BOT_ prefix convention you’ll be able to use the bot_token function (otherwise you’ll have to get these variable from Sys.getenv).

After you’ve finished these steps restart R in order to have working environment variables. You can then create the Updater object as:

updater <- Updater(token = bot_token("RTelegramBot"))

2. The first function

Now, you can define a function that should process a specific type of update:

start <- function(bot, update){
  bot$sendMessage(chat_id = update$message$chat_id,
                  text = sprintf("Hello %s!", update$message$from$first_name))
}

The goal is to have this function called every time the Bot receives a Telegram message that contains the /start command. To accomplish that, you can use a CommandHandler (one of the provided Handler sub-classes) and register it in the updaters’s dispatcher (which is done with the + operator):

start_handler <- CommandHandler("start", start)
updater <- updater + start_handler

3. Starting the Bot

And that’s all you need. To start the bot, run:

updater$start_polling()

Give it a try! Start a chat with your bot and issue the /start command - if all went right, it will reply.