Introduction
In Django, views are used to process HTTP requests and return responses like HTML, JSON, or other data. There are two primary methods to define views: Function-Based Views (FBVs) and Class-Based Views (CBVs).
FBVs are the conventional method where a view is defined as a standard Python function. They are easy, simple to grasp, and perfect for small or low-level logic.
CBVs are based on Python classes and adhere to object-oriented principles. They facilitate reusing and extending code, particularly in sophisticated applications. Django also offers a plethora of generic CBVs with default functionality for typical operations such as viewing or modifying data, eliminating boilerplate code.
Both FBVs and CBVs perform the same function—delivering responses to user requests. The option between them is determined by the level of complexity of your project and your development style.
What is a View in Django?
In Django, a view is either a Python function or class that takes a web request and responds with web response. It is one of the main parts of Django’s Model-View-Template (MVT) framework, where the view handles the logic of the application and what data to present to the user.
A view may produce various types of responses, including:
- An HTML page rendered out of a template
- A redirect to a different page
- JSON/XML data for APIs
- Even non-HTML responses such as an image or file
Views are typically defined within a file called views.py within each Django application by convention.
It should be noted that although Django uses MVT architecture, its views are about equivalent to the controllers of the MVC (Model-View-Controller) pattern because they include the request-handling logic and response-returning logic. In Django, the templates act as views in MVC, as they handle the presentation layer (HTML, CSS, JavaScript).
Types of Views:
- Function-Based Views (FBVs):
- Class-Based Views (CBVs):
Function-Based Views (FBVs):
Function-Based Views (FBVs) are the classical method of view definition in Django. They are actually Python functions that accept an HTTP request and return an HTTP response. Fundamentally, FBVs are simple — it is easy to observe the sequence of logic within the function.
FBVs are simple to learn, easy to use, and beginner-friendly, making them an ideal choice to begin with Django. They even have a tendency to create boilerplate code in large projects, particularly while applying typical patterns such as CRUD operations or dealing with multiple HTTP methods (GET, POST, etc.). This was one of the key reasons why Django introduced Class-Based Views (CBVs) later to minimize boilerplate and encourage code reusability.
In a nutshell, FBVs are easy and convenient for small applications, yet become more difficult to manage as the project expands.
Advantages of Function-Based Views (FBVs)
- Easy to Understand and Simple: Beginner-friendly and easy to use.
- Control Over Code Flow: Explicit control over what occurs for every HTTP method (GET, POST, etc.).
- Versatile: Ideal for one-off or specialized view logic where complete control is required.
- Decorator Compatible: Compatible with decorators such as @login_required, @require_http_methods, or your own custom ones.
- Suitable for Small Projects: Perfect for rapid prototyping or one-off functionality.
- Simplicity: FBVs are easy to understand and implement and smaller projects.
- Familiarity: They use standard Python function syntax, which most developers are already comfortable with.
- Flexibility: Any Python function can be used as a view, allowing easy integration with third-party libraries and custom logic.
Disadvantages of Function-Based Views (FBVs)
- Code Duplication: Repeated boilerplate code frequently results from similar tasks such as form handling or querysets.
- Conditional Branching: Various HTTP methods (GET, POST, etc.) typically involve multiple if conditions, which makes the code more difficult to handle as it expands.
- Limited Reusability: FBVs do not use object-oriented programming (OOP), meaning extending and reusing logic becomes more complex.
Harder to Maintain: FBVs in large projects are more disorganized and harder to scale than CBVs.
Class-Based Views (CBVs):
Class-Based Views (CBVs) come with Django (from version 1.3) as a means of avoiding some of Function-Based Views’ limitations, such as redundant code and unclean conditional branching. Rather than views being implemented as functions, CBVs implement views as Python classes that inherit from Django’s View class.
With CBVs, each HTTP method (GET, POST, etc.) will have its own method in the class, and the code will remain neat and clean. They also utilize object-oriented programming (OOP) principles such as inheritance and mixins, and the code extensibility and reusability become easy.
Advantages of Class-Based Views (CBVs)
- Code Reusability: CBVs follow the DRY principle. Generic operations like object creation, updating, or deletion are wrapped into reusable generic views (e.g., CreateView, UpdateView).
- Better Organization: Each of the HTTP methods (get, post, etc.) is handled in its own method, which is cleaner and easier to maintain than with heavy conditional branching in FBVs.
- Extensibility: CBVs are simple to extend by inheritance or augmented with mixins and can be modularly extended with fresh functionality.
- Built-in Generic Views: Django provides a set of generic CBVs that simplify and speed up development for general CRUD operations.
- Consistency: They offer a consistent and structured way of writing views, ensuring consistency in large projects.
- Make the Most of OOP Concepts: CBVs leverage object-oriented concepts like modularity, inheritance, and reusability to their maximum potential, leading to cleaner and scalable code.
Disadvantages of Class-Based Views (CBVs)
- More Advanced: CBVs add abstraction, which may be harder for novices to follow than simple FBVs.
- Implicit Code Flow: Much of the work is going on in the background (e.g., dispatch() and as_view()), making the code less understandable and even more challenging to debug.
- Mixin Confusion: Applying too many mixins can complicate the code and render it difficult to read and comprehend.
- More Overhead: Can have more imports or method overrides, which are less obvious.
- Decorator Usage: Decorators are not as straightforward to use as FBVs and may involve more steps.
To use the CBV in a URL pattern, you need to convert it to a function using the as_view() method:
Conclusion
There is no strict right or wrong option between Function-Based Views (FBVs) and Class-Based Views (CBVs) in Django. Both are acceptable methods, and it’s up to you to choose the best one based on the situation and needs of your project. FBVs are easy to use, readable, and appropriate for small projects, rapid prototypes, or dealing with special and custom logic. CBVs are better suited to large projects, with better organization, reusability, and intrinsic support for common patterns like CRUD operations. In practice, Django allows you to use either — or even a combination of both — as tends to be most suitable for your application and your style of programming.