Now, we will create a NotificationManager
class that we will use to persist the NotificationModel
instances in an in-memory dictionary. Our API methods will call methods for the NotificationManager
class to retrieve, insert, update, and delete NotificationModel
instances. Create a new service.py
file in the service
folder. The following lines show the code that creates a NotificationManager
class in the service/service.py
file. In addition, the following lines declare all the imports
we will need for all the code we will write in this file. The code file for the sample is included in the restful_python_2_01_01
folder, in the Flask01/service/service.py
file:
from flask import Flask from flask_restful import abort, Api, fields, marshal_with, reqparse, Resource from datetime import datetime from models import NotificationModel from http_status import HttpStatus from pytz import utc class NotificationManager(): last_id = 0 def __init__(self): self.notifications = {} def insert_notification(self, notification): self.__class__.last_id += 1 notification.id = self.__class__.last_id self.notifications[self.__class__.last_id] = notification def get_notification(self, id): return self.notifications[id] def delete_notification(self, id): del self.notifications[id]
The NotificationManager
class declares a last_id
class attribute and initializes it to 0
. This class attribute stores the last ID that was generated and assigned to a NotificationModel
instance stored in a dictionary. The constructor, that is, the __init__
method, creates and initializes the notifications
attribute as an empty dictionary.
The code declares the following three methods for the class:
insert_notification
: This method receives a recently createdNotificationModel
instance in thenotification
argument. The code increases the value for thelast_id
class attribute and then assigns the resulting value to the ID for the received notification. The code usesself.__class__
to reference the type of the current instance. Finally, the code addsnotification
as a value to the key identified with the generated ID,last_id
, in theself.notifications
dictionary.get_notification
: This method receives theid
of the notification that has to be retrieved from theself.notifications
dictionary. The code returns the value related to the key that matches the receivedid
in theself.notifications
dictionary that we are using as our data source.delete_notification
: This method receives theid
of the notification that has to be removed from theself.notifications
dictionary. The code deletes the key-value pair whose key matches the ID received in theself.notifications
dictionary that we are using as our data source.
We don't need a method to update a notification because we will just make changes to the attributes of the NotificationModel
instance that is already stored in the self.notifications
dictionary. The value stored in the dictionary is a reference to the NotificationModel
instance that we are updating and, therefore, we don't need to call a specific method to update the instance in the dictionary. However, in case we were working with a database, we would need to call an update method for our ORM, data repository, or database service.