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An Introduction To MVVM Architecture In Flutter

Sitaram Sharma By Sitaram Sharma | February 14, 2020
introduction to MVVM

Design patterns and architecture of an application attain a great significance in its development. Developers utilize several frameworks like Flutter to implement these elements and enhance the application. In this blog post, you will dive deeper into the significance of Model View ViewModel (MVVM) architecture of Flutter, used for implementing app designs.

With the essence of flexibility and suitability, the MVVM design pattern offers a uniform representation of data. This step is crucial as the wrong architecture can create trouble and might result in handling the whole codebase or the expansion of the application.

Introduced by Microsoft, an MVVM architecture and its elements are becoming essential tools in app development projects. 

Let’s get started with its overview including in-depth meaning and concepts.

What Is MVVM?

As per the definition, MVVM is an abbreviation of three major components combined together, namely Model, View, and ViewModel. The ideology of implementing this architecture is to build a View Model that can represent data through a view.

Here, the View element can utilize data offered by View Model to occupy itself a centralized value. To write an adaptable codebase, android app developers need to build a View-Model layer that can be utilized by several ‘Views’.

MVVM architecture provides platform-friendly design patterns, so they are compatible with any mobile app development framework like Flutter. This architecture mostly used to write WPF (Windows Presentation Foundation) applications.

Given below are the key elements of MVVM Android architecture that help to set up a block for the whole codebase.

The Model

A Model in MVVM design pattern helps to represent the real-time data or information that will be used in the Android app development. A good example to understand this element will be a Phone Number, having a person’s name and address.

For an in-depth understanding, the Model can only reflect the actual data, not the characteristics or any feature related to the application. It means you can’t manipulate the way how the data will be represented or formatted. Each item in the dataset will be representing its own model when the data is fetched.

In certain cases, logics are encapsulated in different classes to keep the Model separate from them. However, these cases are not always true because some of the Models can have validation logic.

The basic aim is to keep the Model ‘Clean’, meaning it should truly represent the data as a ‘Real-world’ implication. For instance, a record of phone numbers can have the last modification details and details of the modifier (user). 

Despite having no relevancy, modified time still possesses as one of the functions of how the Model represents the data. This is how a Model entity actually works.

The View

The View is the interface offered to the users in Model View ViewModel architecture. This element utilizes a set of libraries to present the data more accurately and appropriately.

For instance, a Model contains a Date in the Unix Time for. The View can present data in the form – Month / Date / Year, according to the user’s local time zone. 

This element also possess the property to utilize behaviors associated with the Model, such as identifying and act according to user input. The View can handle the actions done by a user, which can be manipulated by the Model’s functionalities.

Since the View acts according to the gestures or inputs by the users, it has no prescribed knowledge of the Model created in the architecture. However, it attains the properties of the user behaviors and other data bindings acknowledged with the specified Model and ViewModel. 

Even if these user inputs or behaviors aren’t mapped with calling function, properties, and commands, the view will still manage its own responses without getting completely dependant on the ViewModel.

In addition, the View doesn’t have a stable or constant state of action. It synchronizes its behavior with the ViewModel.

The ViewModel

The most essential element of MVVM architecture is ViewModel, which presents the View part separately from the Model. This element makes the Model hold the actual data, and the View part holds the formatted or updated data while keeping the controller as an interface between them.

As an interface, the controller has all the records of user input in the view to place them in the model. Or, it can interact with a function of the View to retrieve the data from the Model, then translating the properties to merge it with the View.

The ViewModel also possesses access to the methods, function calls, and other factors that can help to maintain the actual state of the View. Moreover, this access also allows ViewModel to manipulate or moderate the Model according to the behaviors in the view while triggering its processes.

While building the MVVM design pattern, these elements play a crucial role. As their properties include consistent synchronization with each other, users can have the leverage to interact with the application smoothly.

After getting the introduction to MVVM components, let’s dive deeper into the concepts included in its working.

Abstraction Of The Concepts In MVVM

The View and the ViewModel function differently, still they are interconnected.

However, the question arises that which element should be put first. Most of the developers agree that a single View must possess the connectivity with one ViewModel, not the multiple ViewModels.

To understand the interconnectivity between these elements, let’s have a look on below-given pointers:

The View & The ViewModel

  1. Interaction between these elements held through data-binding, user-centric behaviors, real-time events, and device messages.

  2. Along with the Models, The ViewModel also represents their properties such as state of the activeness and other commands.

  3. The View capitulates its own actions on UI then formulate the events on the ViewModel through commands.

  4. 2-way data binding helps the View to update the Models and properties on the ViewModel.

Data binding is the key factor that initiates the interconnectivity of these elements in the MVVM architecture. This property helps to maintain the flow between UI behavior and the action of elements.

The ViewModel & The Model

In this connectivity, the ViewModel handles how the Model will be represented. Let’s see how:

  1. The ViewModel has control while sharing the Model completely or exposing some of its properties through data binding.

  2. The ViewModel can allow the interaction with services, data compositions, etc at the time of fetching, and have the allowance to manipulate properties in the View.

Furthermore, a View can attain the composition of other Views, having their own ViewModels. Also, ViewModels can constitute more ViewModels, if necessary, to enhance the interconnectivity and interrelation using data bindings.

Implementing MVVM In Flutter Apps

The key objective behind the implementation of the MVVM design pattern is to transfer as much logic as possible from the View element into a separate ViewModel. Through different properties and business logic, these elements serve as the medium between the View and the Model.

The implementation of MVVM Android architecture follows a step-by-step approach to keep the design pattern flexible and responsive.

  • First, the View doesn’t have knowledge about its Controller. The only property these elements posses is how to present data to the user as instructed by View Controller. 
  • Secondly, the view controller doesn’t have knowledge about the model. This factor is important when there is an MVVM vs MVC comparison.
  • The model doesn’t possess the knowledge about its ViewModel. It means the model doesn’t have any clue of its owned properties.
  • Through data binding, the ViewModel owns the Model. However, it is completely opposite in MVC applications.
  • The View and the View Controller owns the properties of the View. This binding remains constant throughout the working of MVVM architecture.
  • And at last, the Controller has the knowledge about the ViewModel. It has consistent interaction with the Model layer via single or multiple ViewModels.

While building design patterns in Android apps through Flutter MVVM architecture, these properties remain constant. The approach is to maintain the consistency in data bindings throughout the architecture.

MVVM architecture

Moreover, there are certain responsibilities that every element should possess. Defining them will help the developers to keep the design pattern effective according to UI behaviors.

The ViewModel possess these responsibilities:

  • It reacts according to the inputs of users.
  • It provides the data as an output through the View.

The View is not supposed to contain any logic or method. So, it takes responsibilities for the following action:

  • The View reacts according to the states of the updated output in the ViewModel and adapts properties accordingly.
  • It conveys the information/data to the ViewModel about every new input.

This approach keeps the architecture quite simple as the ViewModel will only act when there is a change or input is conveyed through the View. This difference makes the implementation of MVVM design patterns easy while developing Android applications.

Now you know the building and implementation of MVVM architecture, it is also necessary for you to know the reasons for doing this. 

There are several aspects it covers to overcome the codebase complexities.

Let’s discuss the points that can describe its importance for your Flutter app development project.

Why MVVM Is Crucial For Your App?

Implementing the code architecture and making the design pattern simplified is the core objective for every developer. This approach solves several problems and delivers a great outcome at the end of the project.

The most common issue that app developers face is the consistency in the whole codebase. Even a small change in a single thread creates plenty of bugs while testing the application. This results in a lack of tight coupling.

MVVM architecture has the capability to overcome these hickups and deliver better design patterns for the app. All the complexities will get a halt with these patterns.

Here are the ways through which it overcomes these hiccups:

Tight Coupling

The very first aim behind implementing a stable design pattern is to keep things in a ‘distributed manner’. This approach can be fulfilled if the relation between different ViewModels is tightly bound.

ViewModels act as simplified classes that can enhance the interaction with the Model layer to represent the data without any knowledge of how this data is consumed. 

Only View(Activity) holds the reference to ViewModel and not vice versa, this solves a tight coupling issue. A single view can hold a reference to multiple ViewModels. Here, the reference to any ViewModel is kept only by the View. As a result, the problem with tight coupling will remain solved.

Testability 

ViewModels in the architecture offers the leverage for running unit tests in apps, which is slightly difficult with the Views. Due to the dependency of this element, initiating the test cases becomes a little complex.

On the other hand, ViewModels can easily represent the data or the state. Hence, they can be tested independently without requiring to know how data is processed. This happens because ViewModels are independent of the Views.

Code Sharing & Usability

If developers are looking forward to deploying the same app on other OS platforms like iOS then sharing an entire codebase is the only solution. It means developers won’t require writing a whole new codebase and can save time by reusing the same codes.

MVVM architecture allows this objective to get fulfilled with the help of Models. This layer can be utilized for building design patterns in other applications as well, without modifying codes.

These advantages lead developers to establish a high-quality design pattern. Implementing Model View ViewModel architecture for Android will result in the hassle-free development of the applications.

All the aspects that you have read above are making this UI tool an essential component in Flutter app development. Even before, it was used in several apps that are now popular in different app marketplaces.

Top Apps Built With MVVM Framework In Flutter

apps built on flutter

If you are looking for a Flutter example app then get through this list of popular mobile apps that have implemented MVVM design pattern.

Google Ads

Google Ads is the most popular application, especially in the digital marketing industry. This Flutter-based application helps marketers to create, manage and optimize online advertising campaigns. It offers real-time data and statistics about all the campaigns. Even it also suggests changes to optimize the campaigns accordingly.

Cryptomaniac Pro

Another popular app is Cryptomaniac Pro, which helps users to get the most accurate data about cryptocurrency. It also shares news and related information through posts to help investors and individuals gain profits.

EntrenaPro

In the fitness category, the Flutter framework also helped developers to build great apps like EntrenaPro. It acts as a stage of interaction for athletes, sports coaches, and sports centers. Users looking for training and coaching in their region are finding this application very useful.

PostMuse

In the photography and editing genre, PostMuse is the popular application built on the Flutter framework. In general, it is an editor through which users can personalize their Instagram posts and stories. It offers a wide range of tools like frames, fonts, filters, emojis, etc. Overall, it is a powerful editor for your personalized gallery.

Pairing

Flutter framework also helped companies to develop engaging social media dating apps. One of them is Pairing, which helps to find the right companion. Users looking for a relationship partner are finding this application very useful and effective.

Final Words…

Developing mobile apps with the Flutter framework provides an enhanced experience to the app developers. As compared to native development, it fulfills every aspect that a developer and an app user can expect.

The key reason behind it is the leverage of using MVVM architecture. With strong design patterns, enhanced data bindings, and sharable Model entities, this framework is a strong companion in building the most enhanced UIs.

This guide is all about understanding the functioning, implementation, and benefits of the Model View ViewModel platform.

Sitaram Sharma
Sitaram Sharma

Co-Founder and VP Mobile Architect of Appventurez. A software professional who is highly experienced in Android, Flutter, React Native. He is a passionate developer with excellent programming skill who believes in bridging the technology gap and making the life of a large number of people much easier through his wide knowledge and experience.

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