Built an App with Object-Oriented an SOLID principles Using Django

Introduction:

Object-Oriented Programming (OOP) is a programming paradigm that offers numerous advantages in software development. By organizing code into objects with properties and behaviors, OOP promotes modularity, reusability, and maintainability. On the other hands, The SOLID principles — Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion — provide valuable guidelines for designing software architectures that are maintainable, extensible, and scalable. Incorporating these principles into your Django projects helps ensure clean code organization, reusability, and flexibility. By embracing SOLID, you establish solid foundations for software development, enabling easier collaboration, efficient maintenance, and future growth. Let’s go into project implementation to understand all the terms

Project Design — Vessel Automated Maintenance System

The Vessel Automated Maintenance System is an information system for ships designed to determine the budget required for maintenance over a specific period and identify the necessary equipment and maintenance services. This system provides a visualization of the estimated total maintenance budget over a given time range for ship owners. It also assists the chief engineer assigned to a ship in monitoring the ship’s status to quickly detect issues and plan maintenance work for a specific operational period.

The system utilizes a database to store data related to ships, owners, and chief engineers. More detailed information, such as the usage hours of ship components, can be periodically updated by the assigned chief engineer. The system then performs computations and presents the results related to maintenance work through a web application.

In summary, the Vessel Automated Maintenance System serves as a comprehensive tool for ship owners and chief engineers. It facilitates budget estimation, helps track the ship’s status, identifies necessary maintenance tasks, and provides relevant information for planning and executing maintenance work. The system enhances efficiency, enables proactive maintenance, and improves decision-making in ship maintenance processes. Let’s create the database design:

Vessel Database Design

The provided describes a data logic on vessel maintenance system. We can analyze how these principles can be applied in the context of these databases:

Single Responsibility Principle (SRP):

Each use case represents a specific functionality or action performed by a primary actor (e.g., Ship Owner, Chief Engineer, Admin). This aligns with the SRP as each use case has a clear responsibility and encapsulates a single action.

Open/Closed Principle (OCP):

The use cases describe the ability to view maintenance cost overviews, vessel status, search and filter vessels, generate maintenance forecasts, input vessel and component running hours, and modify data in the database. These use cases demonstrate the system’s openness for extension by accommodating various maintenance-related functionalities.

Liskov Substitution Principle (LSP):

The use cases involve different actors interacting with the system, such as Ship Owners, Chief Engineers, and Admins. The LSP would apply by allowing subclasses or specific actor roles to substitute the base actor role when interacting with the system.

Interface Segregation Principle (ISP):

The use cases cater to the specific needs of different actors, such as Ship Owners wanting to view cost overviews, Chief Engineers monitoring vessel status, and Admins modifying database data. This aligns with the ISP as the system provides interfaces tailored to the requirements of each actor.

Dependency Inversion Principle (DIP):

The use cases involve interactions between actors and the system, where dependencies on specific implementations (e.g., database) are abstracted through interfaces. This promotes flexibility, allowing different implementations to be used without affecting the use cases’ functionality.

Overall, while the provided design on the functional aspects of the vessel maintenance system, we can observe how OO principles and SOLID principles can be applied to ensure proper design, modularity, and extensibility of the system. By adhering to these principles, the system can be built with code that is easier to maintain, test, and evolve over time. Now let’s look implement it on the Django

Django Implementation

To implement the vessel maintenance system described earlier in Django, you would need to create Django apps to held the models, views, templates, and forms.

Certainly! Let’s dive deeper into the OOP aspects of the Django project based on the provided folder structure:

Models:

• The “models.py” file in each app’s directory (e.g., “vessels”, “users”, “work_orders”) contains Django model classes. These model classes define the structure and behavior of the application’s data entities, such as vessels, users, and work orders.
• Each model class represents a table in the database, and its attributes define the fields/columns of that table. The attributes can include fields like CharField, IntegerField, DateTimeField, ForeignKey, etc., representing the data types and relationships between entities.
• The model classes encapsulate the data and provide methods to interact with the database, such as creating, retrieving, updating, and deleting records. They allow for object-oriented manipulation of data and follow the principles of encapsulation and data abstraction.

Views:

• The “views.py” file in each app’s directory contains view functions or classes that handle HTTP requests and define the logic for processing those requests.
• Each view function or class represents a specific endpoint or URL pattern and performs actions based on the request type (GET, POST, etc.). These views interact with models to retrieve data, perform operations, and render appropriate responses, such as returning HTML templates or JSON data.
• View functions or classes can encapsulate reusable behavior, such as authentication, authorization, input validation, and data transformation, following the principles of modularity and reusability in OOP.

Serializers:

• The “serializers.py” file in each app’s directory contains serializer classes. Serializers handle the conversion of complex data, such as model instances, into formats suitable for transmission over the network, such as JSON.
• Serializers define the structure and rules for data validation, transformation, and serialization/deserialization. They provide methods like “serialize,” “validate,” and “create” to convert complex objects into JSON and vice versa.
• By separating the serialization logic into serializer classes, Django promotes the principles of separation of concerns and single responsibility, making it easier to customize the data representation and handle complex data operations.

URLs:

• The “urls.py” file in each app’s directory contains URL patterns and their associated views. It defines the routes and URL patterns for accessing different views in the application.
• URL patterns map URLs to specific view functions or classes, allowing the application to handle requests based on the provided URL. This mapping follows the principles of encapsulation and loose coupling between the URL structure and view logic.
• The URL patterns can use regular expressions or path patterns to capture dynamic segments of the URL, enabling flexible routing and parameter passing.

Apps:

• Each app’s directory includes the “apps.py” file, which defines the configuration and metadata for that app.
• The app configuration includes settings like the app’s name, label, icon, and other metadata. It allows Django to recognize and manage the app independently, facilitating modular development, pluggability, and code organization.
• The app configuration follows the principles of encapsulation and modularity, enabling easy integration of reusable apps within the Django project and separation of concerns between different functional components.

Conclusion

Overall, the Django project’s folder structure embraces object-oriented programming principles such as encapsulation, modularity, separation of concerns, and reusability. The structure encourages the creation of self-contained components (models, views, serializers) that encapsulate specific functionality, promoting code organization, maintainability, and extensibility.

By integrating Object-Oriented Programming (OOP) and SOLID principles in your Django project, you can ensure your codebase is not only easy to maintain and extend, but also that it adheres to best practices in software development. Utilizing the power of Django, a powerful Python web framework, combined with a well-structured and principled approach to design, can help you build robust and efficient applications.

In the context of the Vessel Automated Maintenance System, we’ve seen how these principles can be applied in database design, use case identification, and implementation. Django’s inherent structure and capabilities already align very well with these principles, providing a solid foundation for your project.

Models encapsulate the data and its behavior, views handle HTTP requests and response logic, serializers manage data validation and transformation, and URL configurations define routing rules and patterns. All these components work together harmoniously, following principles of encapsulation, modularity, and single responsibility, demonstrating the benefits of OOP and SOLID principles in action.

The SOLID principles guide you to design classes that are robust, easy to change, and easy to understand. Applying these principles in your Django applications enables you to write clean, maintainable code that can be easily extended or modified without causing a ripple effect of changes.

Remember, although these principles provide a useful guideline, they are not hard and fast rules. Use them wisely, and always consider the specific requirements and constraints of your project. The ultimate goal is to create software that not only works but is also easy to understand, modify, and maintain.

By continuously learning and practicing these principles, you can improve your software design skills and become a better programmer. The vessel maintenance system built in Django is just one example. There are many more areas where you can apply these principles to improve your software design.