Design a Parcel Tracking System for OOD Interviews

When designing a Parcel Tracking System using Object-Oriented Design (OOD) principles, we will focus on a system that allows users to track parcels, manage their statuses, and ensure that the system is extensible for future features. Below is a high-level breakdown of the classes and their responsibilities.

1. Class Diagram Overview

Here’s the key to understanding the system’s components:

• Parcel: Represents the individual parcel to be tracked.

• Shipment: Represents the shipment containing one or more parcels.

• User: Represents the people who will interact with the system, such as customers and administrators.

• TrackingSystem: The core system that manages parcels, shipments, and their status updates.

• Location: Represents the geographical location where a parcel is at any given time.

• ParcelStatus: Enum or Class representing the different states a parcel can be in.

• Courier: Represents the courier responsible for delivering the parcel.

• Notification: Handles notifications sent to users regarding the parcel’s status.

2. Classes and Responsibilities

Parcel

• Attributes:

  • parcelID: Unique identifier for the parcel.

  • weight: The weight of the parcel.

  • dimensions: The dimensions of the parcel (Length, Width, Height).

  • status: Current status of the parcel (e.g., “In Transit”, “Delivered”, “Pending”).

  • shipment: The shipment to which this parcel belongs.

• Methods:

  • updateStatus(): Update the status of the parcel.

  • getTrackingInfo(): Fetches tracking details (e.g., location, status).

  • getEstimatedDeliveryTime(): Calculate the estimated delivery date based on current location and status.

Shipment

• Attributes:

  • shipmentID: Unique identifier for the shipment.

  • sender: User who is sending the shipment.

  • receiver: User who is receiving the shipment.

  • parcels: List of Parcel objects associated with this shipment.

  • courier: The Courier assigned to deliver the shipment.

  • origin: The location where the shipment started.

  • destination: The location where the shipment is being sent.

• Methods:

  • addParcel(parcel): Adds a parcel to the shipment.

  • removeParcel(parcel): Removes a parcel from the shipment.

  • getShipmentDetails(): Returns detailed information about the shipment.

User

• Attributes:

  • userID: Unique identifier for the user.

  • name: Name of the user.

  • email: Email address of the user.

  • address: Address details for delivery.

• Methods:

  • requestShipment(shipment): Request a new shipment.

  • viewTrackingInfo(parcelID): Fetch tracking information for a parcel.

  • receiveNotification(notification): Receives updates about their shipments.

TrackingSystem

• Attributes:

  • parcels: A collection of all parcels being tracked.

  • shipments: A collection of all shipments being processed.

• Methods:

  • addParcel(parcel): Adds a new parcel to the system.

  • addShipment(shipment): Adds a shipment to the system.

  • getParcelTrackingInfo(parcelID): Retrieves tracking info for a specific parcel.

  • updateParcelStatus(parcelID, newStatus): Updates the status of a parcel.

  • sendNotification(user, message): Sends a notification to a user.

Location

• Attributes:

  • locationID: Unique identifier for the location.

  • address: Address of the location.

  • latitude: Latitude of the location.

  • longitude: Longitude of the location.

• Methods:

  • getLocationInfo(): Returns information about the location.

  • isInTransit(): Checks if a parcel is in transit at this location.

ParcelStatus (Enum)

Defines the various statuses a parcel can have:

• Pending: The parcel is ready to be shipped but has not yet left.

• InTransit: The parcel is in transit to the destination.

• OutForDelivery: The parcel is out for delivery.

• Delivered: The parcel has been delivered to the recipient.

• Returned: The parcel has been returned due to a failed delivery attempt.

Courier

• Attributes:

  • courierID: Unique identifier for the courier.

  • name: Name of the courier.

  • currentLocation: Current location of the courier.

• Methods:

  • updateLocation(location): Updates the current location of the courier.

  • assignParcel(parcel): Assigns a parcel to a courier for delivery.

  • getDeliveryDetails(): Retrieves the details of parcels the courier is assigned to deliver.

Notification

• Attributes:

  • message: The content of the notification.

  • timestamp: When the notification was sent.

  • recipient: The user receiving the notification.

• Methods:

  • send(): Sends the notification to the user.

  • displayNotification(): Displays the notification to the user.

3. Interactions Between Classes

• TrackingSystem will act as the central controller, interacting with all the other components.

• Users will interact with the TrackingSystem to check tracking info, update the parcel status, or receive notifications.

• Parcel will update its own status and location whenever its status changes, and the TrackingSystem will handle these updates.

• Courier will update the TrackingSystem with their current location and parcel status to keep users informed.

4. Example Flow:

1. Shipment Creation:

   • User creates a shipment via the TrackingSystem, adding parcels to it.

   • The system assigns a Courier to the shipment.

2. Status Update:

   • The Courier updates the parcel’s location and status.

   • The TrackingSystem notifies the relevant User via the Notification class about the change in status.

3. Parcel Tracking:

   • Users can track their parcel in real-time by querying the TrackingSystem for updates on their parcel’s current status and location.

4. Delivery:

   • When the parcel reaches the destination, the Courier delivers it, and the TrackingSystem updates the parcel’s status to Delivered.

   • The User receives a notification that their parcel has been delivered.

5. Extensibility Considerations

• Support for Multiple Couriers: The system can be extended to allow multiple couriers, each with their own fleet of delivery vehicles.

• International Shipments: The Location class can be extended to handle international addresses, time zones, and multiple countries.

• Package Customization: Users can specify different delivery methods or options, such as expedited shipping, fragile items, etc.

This design is flexible and supports future changes, ensuring the system is scalable and maintainable over time.