Get user location in Facebook messenger bots

Requirements

Before we start you need to create a Facebook app for your bot and a page which users will contact to interact with the bot .For a detailed step by step tutorial on how to do that see this tutorial .

You also need ,either

• To setup a new server to host your messenger bot code (You can use Heroku free tier ) or
• Use ngrok to publicly expose your local host to the Internet (So your server can receive realtime updates from Facebook)

When developing your bot ,the recommended way is to use ngrok and develop your bot on your local machine until you finish iterating then you can use a hosting server for production (Heroku or delta now for Node.js hosting)

I'm using Node.js but feel free to use any programming language for web development you are comfortable with ,
Such as PHP ,see this tutorial on how to create a Facebook messenger bot using PHP or Python ,feel free to check this tutorial how to build messenger bots with Python.

The purpose of this tutorial is to show you how to use the user location in messenger bots so you can offer a custom experience to your bot users .This tutorial doesn't cover every step we need to do to create a bot with Node.js . For a complete and step by step tutorial see how to build messenger bots with JavaScript and Node.js

How to get user location

To get the user location ,the user must send the location ,unfortunately this is only available on messenger app for mobile .

So we will start by asking the user to send his location .We can do that for example in the first message

You can also use quick replies to enable users to easily send their location .

This is the web hook to subscribe to Facebook realtime updates

app.post('/webhook', function (req, res) {
var data = req.body;

// Make sure this is a page subscription
if (data.object === 'page') {

    // Iterate over each entry - there may be multiple if batched
    data.entry.forEach(function(entry) {
    var pageID = entry.id;
    var timeOfEvent = entry.time;

    // Iterate over each messaging event
    entry.messaging.forEach(function(event) {
        if (event.message) {
        receivedMessage(event);
        } else {
        console.log("Webhook received unknown event: ", event);
        }
    });
    });

    res.sendStatus(200);
}
});

Here is the implementation of the receivedMessage function to process incoming events .

function receivedMessage(event) {
    var senderID = event.sender.id;
    var recipientID = event.recipient.id;
    var timeOfMessage = event.timestamp;
    var message = event.message;
    var messageId = message.mid;
    var messageText = message.text;
    var messageAttachments = message.attachments;
    if (messageText) {
        var msg = "Hi ,I'm LocationBot ,and I was created to echo back your latitude and longitude coordinates "+
                  "You just need to send me your location  \n" + 
                  "Using the send location button on messenger (only available on mobile devices) \n"+

        switch (messageText) { 
            case 'getstarted' :
                sendTextMessage(senderID, msg);   
            default:
                sendTextMessage(senderID, msg);
        }

    } else if (messageAttachments) {
            var lat = null;
            var long = null;
            if(messageAttachments[0].payload.coordinates)
            {
                lat = messageAttachments[0].payload.coordinates.lat;
                long = messageAttachments[0].payload.coordinates.long;
            }

            var msg = "lat : " + lat + " ,long : " + long + "\n";

            sendTextMessage(senderID, msg);

        }
}

Bots can not start a conversation with users ,this is a counter measure to prevent spam so you need to initiate the conversation with your bot ,in our case we start by sending 'getstarted' message to the bot .The bot then will send you a message in which he identifies itself

"Hi ,I'm LocationBot ,and I was created to echo back your latitude and longitude coordinates "+
"You just need to send me your location  \n" + 
"Using the send location button on messenger (only available on mobile devices) \n"

And asks the user to send his location using the messenger send button .

Well I know this is not the best thing to do so you have better options .You can either :

• Send this message whenever the user sends a message other than his location
• 
  Or add Get Started button to your bot which doesn't produce any misunderstanding for the user in his first experience with the bot .

For the sendMessage logic see build messenger bots with Node.js tutorial

Now lets understand the logic behind getting the sent user location .

We first get the message from the event

var message = event.message;

Then we check if it is a text message or a message with an attachment because the location is sent as an attachment

if(message.text)
{
    // it is a text message 
}
else if(message.attachments)
{
    //It is a possible location message
}    

So if it is a message with attachments we need to check if the first attachment has a payload with a coordinates object and then get latitude and longitude from the coordinates object .

if(message.attachments[0].payload.coordinates){
    // It is a location object
    var lat = message.attachments[0].payload.coordinates.lat;
    var long = message.attachments[0].payload.coordinates.long;
}

Conclusion

Bots are the new apps for the social media era .Combining them with other features such as the user location enables us to offer better experiences to users .

I hope the tutorial was helpful for you and see you on other tutorials .If you have any questions or suggestions please don't hesitate to drop a comment below .

• Date: 02 Mar 2017