User Notifications

The requirement for a notification area came up when I was implementing Event-Role invites feature. For not-existing users that were not registered in our system, an email with a modified sign-up link was sent. So just after the user signs up, he will be accepted as that particular role. Now for users that were already registered to our platform a dedicated area was needed to let the user know that he has been invited to be a role at an event. Similar areas were needed for Session invites, Call for papers, etc. To take care of these we thought of implementing a separate notifications area for the user, where such messages could be sent to registered users. Issue

Base Model

I kept base db model for a user notification very basic. It had a user field that would be a Foreign key to a User class object. title and message would contain the actual data that the user would read. message can contain HTML tags, so if someone wants to display the notification with some markup he could store that in the message. The user might also want to know when a notification was received. The received_at field stores a datetime object for the same purpose.

There is also has_read field that was later added. It stores a boolean value that tells if the user has marked the notification as Read.

class Notification(db.Model):
    """
    Model for storing user notifications.
    """

    id = db.Column(db.Integer, primary_key=True)

    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    user = db.relationship('User', backref='notifications')

    title = db.Column(db.String)
    message = db.Column(db.Text)
    action = db.Column(db.String)
    received_at = db.Column(db.DateTime)
    has_read = db.Column(db.Boolean)

    def __init__(self,
                 user,
                 title,
                 message,
                 action,
                 received_at,
                 has_read=False):
        self.user = user
        self.title = title
        self.message = message
        self.action = action
        self.received_at = received_at
        self.has_read = has_read

action field helps the Admin identify the notification. Like if it is a message for Session Schedule change or an Event-Role invite. When a notification is logged, the administrator could tell what exactly the message is for.

Unread Notification Count

The user must be informed if he has received a notification. This info must be available at every page so he doesn’t have to switch over to the notification area to check for new ones. A notification icon at the navbar perhaps.

Screenshot from 2016-07-19 02:00:47

The data about this notification count had to be available at the navbar template at every page. I decided to define it as a method in the User class. This way it could be displayed using the User object. So if the user was authenticated, the icon with the notification count could be displayed.

class User(db.Model):
    """User model class
    """
    # other stuff
    
    def get_unread_notif_count(self):
        return len(Notification.query.filter_by(user=self,
                                                has_read=False).all())
{% if current_user.is_authenticated %}
    <!-- other stuff -->

    <li>
             <a class="info-number" href="{{ url_for('profile.notifications_view') }}">
                  <i class="fa fa-envelope-o"></i>
                  <span class="badge bg-green">{{ current_user.get_unread_notif_count() | default('', true) }}</span>
             </a>
    </li>

    <!-- other stuff -->

{% endif %}

If the count is zero, count number is not displayed.

Possible Enhancement

The notification count comes with the HTML generated by the template at the server. So to check for new notifications the user must either refresh the page or travel to another page. To show newly received notifications without refreshing the page the WebSocket API can be used. I’ve it in my bucket list and I’ll implement it soon.