Flask-RESTful uses resources built on top of Flask pluggable views as the main building block for a RESTful API. We just need to create a subclass of the flask_restful.Resource class and declare the methods for each supported HTTP verb.

First, we will create a Notification class that we will use to represent the notification resource. Open the service/service.py file created previously and add the following lines. The code file for the sample is included in the restful_python_2_01_01 folder, in the Flask01/service/service.py file:

class Notification(Resource): 
    def abort_if_notification_not_found(self, id): 
        if id not in notification_manager.notifications: 
            abort( 
                HttpStatus.not_found_404.value,  
                message="Notification {0} doesn't exist".format(id)) 
 
    @marshal_with(notification_fields)def get(self, id): 
        self.abort_if_notification_not_found(id) 
        return notification_manager.get_notification(id) 
 
    def delete(self, id): 
        self.abort_if_notification_not_found(id) 
        notification_manager.delete_notification(id) 
        return '', HttpStatus.no_content_204.value 
 
    @marshal_with(notification_fields)   def patch(self, id): 
        self.abort_if_notification_not_found(id) 
        notification = notification_manager.get_notification(id) 
        parser = reqparse.RequestParser() 
        parser.add_argument('message', type=str) 
        parser.add_argument('ttl', type=int) 
        parser.add_argument('displayed_times', type=int) 
        parser.add_argument('displayed_once', type=bool) 
        args = parser.parse_args() 
        print(args) 
        if 'message' in args and args['message'] is not None: 
            notification.message = args['message'] 
        if 'ttl' in args and args['ttl'] is not None: 
            notification.ttl = args['ttl'] 
        if 'displayed_times' in args and args['displayed_times']
 is not None: 
            notification.displayed_times = args['displayed_times'] 
        if 'displayed_once' in args and args['displayed_once'] is
 not None: 
            notification.displayed_once = args['displayed_once'] 
        return notification 

The Notification class is a subclass of the flask_restful.Resource superclass and declares the following three methods that will be called when the HTTP method with the same name arrives as a request on the represented resource:

As previously explained, the three methods call the internal abort_if_notification_not_found method, which receives the ID for an existing NotificationModel instance in the id argument. If the received id is not in the keys of the notification_manager.notifications dictionary, the method calls the flask_restful.abort function with HttpStatus.not_found_404.value as the http_status_code argument and a message indicating that the notification with the specified ID doesn't exist. The abort function raises an HTTPException exception for the received http_status_code and attaches the additional keyword arguments to the exception for later processing. In this case, we generate an HTTP 404 Not Found status code.

Both the get and patch methods use the @marshal_with decorator, which takes a single data object or a list of data objects, and applies the field filtering and output formatting specified as an argument. The marshalling can also work with dictionaries (dict). In both methods, we specified notification_fields as an argument and, therefore, the code renders the following fields: id, uri, message, ttl, creation_date, notification_category, displayed_times, and displayed_once.

The following return statement with the @marshal_with(notification_fields) decorator returns an HTTP 200 OK status code because we didn't specify any status code after the returned object (notification):

return notification 

The next line is the code that is actually executed with the @marshal_with(notification_fields) decorator and we can use it instead of working with the decorator:

return marshal(notification, resource_fields), HttpStatus. HttpStatus.ok_200.value 

For example, we can call the marshal function as shown in the previous line, instead of using the @marshal_with decorator, and the code will produce the same result.

Now, we will create a NotificationList class that we will use to represent the collection of notifications. Open the service/service.py file created previously and add the following lines.

The code file for the sample is included in the restful_python_2_01_01 folder, in the Flask01/service/service.py file:

class NotificationList(Resource): 
    @marshal_with(notification_fields) 
    def get(self): 
        return [v for v in
notification_manager.notifications.values()] 
 
    @marshal_with(notification_fields) 
    def post(self): 
        parser = reqparse.RequestParser() 
        parser.add_argument('message', type=str, required=True, help='Message cannot be blank!') 
        parser.add_argument('ttl', type=int, required=True,
help='Time to live cannot be blank!') 
        parser.add_argument('notification_category', type=str, required=True, help='Notification category cannot be blank!') 
        args = parser.parse_args() 
        notification = NotificationModel( 
            message=args['message'], 
            ttl=args['ttl'], 
            creation_date=datetime.now(utc), 
            notification_category=args['notification_category'] 
            ) 
        notification_manager.insert_notification(notification)  
        return notification, HttpStatus.created_201.value 

The NotificationList class is a subclass of the flask_restful.Resource superclass and declares the following two methods that will be called when the HTTP method with the same name arrives as a request on the resource represented:

The following table shows the method of our classes createdpreviously that we want to be executed for each combination of HTTP verb and scope: