Models, views, viewmodels? What are these concepts and how can they help you design software?

Modern applications need such a variety of features that the process of developing them has grown in size and complexity. To help out, you can use an architectural design pattern. They support the building of applications that are easy to test and maintain.

The three most popular design patterns are MVC, MVP, and MVVM. The MVC stands for model, view, and controller, whereas MVP stands for model, view, and presenter, and MVVM for model, view, and view model.

An architectural pattern clarifies and defines some crucial components of a software architecture. Even though an architectural pattern conveys an image of a system, it is not an architecture. In fact, it is a general and reusable solution to a commonly occurring problem in software architecture in a certain context.

A design pattern is a formalized best practice that you can use to solve common problems when designing an application or system.

Let's start with the common term—pattern. In software, a pattern is a recurrent property that lets you break down a huge and complex structure into smaller, simpler components. You can use this pattern to craft a general solution for a class of problems.

In each level of software development, you’ll use different tools. At smaller levels, these tools are design patterns. Architectural patterns exist at larger levels, and programming paradigms at the implementation level.

During software development, you can use architectural design patterns to solve common problems. Good architecture can also help you to:

But without an architectural pattern, you may face difficulties maintaining your app’s business logic.

Before you look at each pattern, here are the terms that make them up:

The MVC architectural pattern was the first, and it’s popular today in the field of web applications. It was introduced in the 1970s. This pattern lets you build an application around Separation of Concerns (SoC). It eases the effort you need to test, maintain, and develop your application.

In the MVC pattern, the model has no understanding of the view or the controller. The model's observer will receive an alert whenever there's a change in the view and controller. The controller helps the routing process to connect the model to the relevant view.

Some of the MVC pattern's advantages are:

Here’s how MVC works:

Due to the SoC, MVC can reduce the code size and make a good code that is clean and manageable.

The MVP pattern shares two components with MVC: model and view. It replaces the controller with the presenter. The presenter—as its name implies—is used to present something. It allows you to mock the view more easily.

In MVP, the presenter has the functionality of the "middle-man" because all presentation logic is pushed to it. The view and presenter in MVP are also independent of one another and interact via an interface.

Here's an illustration of how the MVP pattern works:

The presenter receives input from the user via the view. It then processes the user’s actions with the help of the model, passing the results back to the view. The presenter communicates with the view through interfaces.

MVVM is the modern evolution of MVC. The main goal of MVVM is to provide a clear separation between the domain logic and presentation layer. MVVM supports two-way data binding between the view and viewmodel.

The MVVM pattern allows you to separate your code’s view and model. This means that when the model changes the view doesn’t need to, and vice-versa. Using a viewmodel, you can do unit testing and test your logic behavior without involving your view.

Here's an illustration of how MVVM works:

Now that you’ve learned about each pattern, find out when to use them.

MVC is simply an implementation of Separation of Concerns. If your application needs to separate the data (model), the data crunching (controller), and data presentation (view), MVC will work well. MVC also serves well in an application where the data source and/or the data presentation can change at any time.

You can use MVP when your application has a bidirectional flow. If user interactions need to request something from the model, and the result of this request will change the UI immediately, consider MVP.

You'll want to use MVVM when:

The main reason to use a design pattern is to reduce complexity. You can do this by reducing overall complexity or by replacing unfamiliar complexity with the familiar. If a design pattern cannot reduce complexity in either of those two ways, do not use any of it; it will not add any value whatsoever.

If you’re really sure that you should use a design pattern, try to make a checklist. Base it on the situations you've seen here and choose the best fit for your project.

Rosa is a writer who has a high enthusiasm for all aspects of STEM and always uses her writing as her medium to share her knowledge with others. Besides writing, she also loves to design, code, or just listen to music.

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