Uploading Images via APIs in the Open Event Server

Posted: 2017-08-15T17:52:00+05:30
APIs help us to send and receive data in some particular data format that can then be used individually or integrated with a frontend UI. In our case, the entire API server is used to manage all the requests from the frontend and send back the necessary response. Usually, the application is to send simple form data which is then stored into the backend database and a valid jsonapi response is shown. However other than normal text, url, datetime data one very important data is media files, in our case event images, user images, slides, etc. In this blog, we will particularly deal with how we can upload images in the server using API.

Sending Data

Firstly, we need to decide how do we send the data in the post request of the API. So we are sending a base64 encoded string representing the image along with the image extension appended to it, for example, data:image/png;base64,iVBORw0KGgoAAAANS. This is a widely used format for showing images over the web. So when we send a POST request we send a json encoded body like:

"data": "data:image/png;base64,iVBORw0KGgoAAAANS"

Converting Base64 Data to Image

There are 2 parts of the data in the string that we receive. The first part basically tells us the format of the image(.gif in this case) and string encoding(base64 in this case), the second part gives us the encoded string. So, from the first part, we extract the file extension for the image file to be created. We use uuid.uuid4() for a random filename.
filename = '{}.{}'.format(str(uuid.uuid4()).data.split(";")[0].split("/")[1])

Now to write the base64 encoded string as an image file, we first need to get only the encoded string part from the data and then decode it. We use string decode function of python for the decoding purpose. Then we write the data to the image file and save it.

API Response

Finally using whatever logic you are using for serving your static files, you generate the static file path for the image saved. And then create another json encoded response which returns you the url for the saved image in the server.
"url": "https://xyz.storage.com/asd/fgh/hjk/1233456.png"

And there you have your image uploaded and served.


Autocomplete Address Form using Google Map API

Posted: 2016-09-29T18:01:00+05:30

Google map is one of the most widely used API of Google as most of the websites use Google map for showing address location. For a static address it's pretty simple. All you need to do is mention the address and the map will show the nearest location. Problem arrives when the address is dynamically putted by the user. Suppose for an event in event organizer server, one enters the location. The main component used while taking input location is Google Autocomplete. But we went a step further and parsed the entire address based on city, state, country, etc. and allowed user to input the details as well which gave them the nearest location marked in Map if autocomplete couldn't find the address.
Autocomplete Location
Screenshot from 2016-07-27 06:52:37
As we can see, in the above input box we get suggestions by Google Map on entering first few letters of our address. To this, we need the API https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=places&callback=initMap. You can find an example code of how to do this here.
After this is done, what we wanted is not to just include this address, but to provide a form to fill up the entire address in case some parts were missing on this address. The function that the autocomplete listens to is "place_changed" . So once we click on one of the options, this event is triggered. Once the event is triggered, we use the autocomplete.getPlace() to get the complete address json. The json looks something like this:
Screenshot from 2016-07-27 07:04:49
Now what we do is we create a form with input fields having the id same as the ones we require(e.g., country, administrative_area_level_1, locality, etc.). After that we select the long_name or the short_name from this json and put the value in the corresponding input field with the ids. The code for the process after getting the json is elaborated here.

Editing Address Form

After doing this it looks something like this:
Screenshot from 2016-07-27 07:12:13
However, now the important part is to show the map according to this fields. Also, every time we update a field, the map should be updated. For this we use a hack. Instead of removing the initial location field completely, we hide the field but keep the binding to autocomplete intact. As a result the map is shown when we select a particular address.
Now when we update the fields in the address form, we append the value of this field to the value in the initial location field. Though the field is hidden but it is still bound to autocomplete. As a result as soon as we append something to the string contained in the field, the map gets updated. Also, the updated value gets stored to the DB. Thus, with every update in field, the pointer is moved to the nearest location formed by appending all the data from the form.
After saving the location data to DB, if we wish to edit it, we can get back the json by making the same request with the location value. And then we will get back the same address form and the map accordingly.
Finally it looks something like this:
Screenshot from 2016-07-27 07:19:56


Sending Email using Sendgrid API

Posted: 2016-07-09T16:47:00+05:30
One of the important features while creating server side code for some website/ web application is sending emails. But how do we send emails. There are different ways and packages using which you can setup SMTP ports and send emails. So why specifically sendgrid? Because along with SMTP relay, sendgrid also allows you to send emails using its Web API which makes work much easier. Here, we will discuss about using Web API.

SendGrid’s Web API sends mail via HTTP. Your server sends a message to SendGrid, and receives either a 250 message, indicating that the message was accepted by the receiving server, or a 400 or 500 message, indicating that something is wrong, prohibiting us from processing the request.
When everything is packaged correctly, SendGrid can process the request and then send it to the intended recipient’s ISP that responds with either a 250 message or a 500 message of their own, informing SendGrid whether or not the message was received. This process is more similar to putting your package in the mailbox and letting the post office review its information and deliver it for you.
Some sample requests:
 curl -X "GET" "https://api.sendgrid.com/v3/templates" -H "Authorization: Bearer Your.API.Key-HERE" -H "Content-Type: application/json"
POST https://api.sendgrid.com/v3/templates/ HTTP/1.1
Content-Type: application/json
"name": "new template name"
HTTP/1.1 200 OK
Content-Type: application/json
"foo": "bar",
You can go through the various errors from this link: https://sendgrid.com/docs/API_Reference/Web_API_v3/How_To_Use_The_Web_API_v3/errors.html

An example request for email is:
POST https://api.sendgrid.com/v3/mail/send HTTP/1.1
Request body:-
"personalizations": [
"to": [
"email": "john@example.com"
"subject": "Hello, World!"
"from": {
"email": "from_address@example.com"
"content": [
"type": "text",
"value": "Hello, World!"
HTTP/1.1 202