As smartphones and tablets are getting popular, the operating systems for these devices are becoming more important. Every software development procedure requires different technologies, design and architecture patterns to help with the specific needs of customers and provide viable solutions to them. The main aim of such design patterns is to help in developing applications that have loose architecture and are easy to maintain and test. The MVC, MVP, and MVVM are considered to be the three main popular design patterns, wherein, the MVC stands for model view controller, MVC stands for Model View Presenter, and MVVM stands for Model view view-model. When we build an application in an organized manner with proper functionalities and implement it with proper protocols, then it is called an Architecture.
Why do we need architecture?
If we don't use architecture, we might fall under the risk of writing our codes in an unorganized pattern. This might increase the number of lines of code, making it difficult to understand. It also decreases readability and increases the number of bugs. So, to provide clear data flow which increases robustness, scalability, bug resistance, increases readability, we should use proper architecture, suitable to work in a team.
The architectural patterns provide the best practices and play a significant role in application development. These patterns are designed to simplify the complex codes and make the UI code cleaner and manageable. Let us see how:
The software architectural design pattern ensures organized programming. It also separates application functionality which is easy to test and provides low-cost maintenance. MVC, MVP & MVVM are some popular architecture patterns that companies follow for mobile & web app development. It is considered that the MVC is ruled out by the much conventional MVP and MVVM patterns.
Let’s take a look at Model View Controller (MVC), Model View Presenter (MVP) and Model View View-model (MVVM) one by one.
Model View Controller (MVC) Pattern
It is a software design pattern that makes creating huge applications easy. This pattern has been used and extensively tested over multiple languages and generations of programmers. Even though it does not belong to a specific framework, it is able to create any kind of application or software in any programming language. In MVC, the controller is responsible for determining which view to display in response to any action, including when loading the application.
MVC is an architectural pattern that was the first option for web application designing. MVC builds the application in a way where the layers in concern are separated. This minimizes all the efforts needed to extend, test and maintain the application. The process maximizes the size of view class among UI, data binding logic and business operations. To sum up, the MVC architecture pattern works towards reducing the size of code making them easily manageable and cleaner. It is very commonly used in architecture. However, it is considered that the MVC is ruled out by the much conventional MVP and MVVM patterns.
The MVC design pattern separates an application into three major components:
Model, View, and Controller.
Model works directly with the database. It is the model where all the application's data are stored. It contains only pure application data without having to deal with the user interface or data processing. The Model describes the business logic and it is characterized by a set of classes. It works on designing business rules for data on how the data is changed or handled. The model does not have any knowledge about the view and the controller. It typically notifies its observers about any change that has occurred.
The view presents the model’s data to the customer/user on which they can perform some actions. Basically it is the View that represents what’s presented to the users and how they interact with the app. It contains HTML, CSS, JS, XML or any other markup language that is used to create a beautiful user interface. It involves code to show the data that it receives from the application and then respond to the events. It communicates with the controller and at times interacts with the model.
Controller is the most important part of the architecture. It is the decision-maker and exists between the view and the model. The controller updates the View whenever the model changes. The controller processes the data after we get a request from the view and before updating anything in our database with the Model. It is a fragment that communicates with view and model by taking the user input from view.
Advantages of MVC Architecture
MVC architecture accelerates development in parallel. It allows developers to work on the components simultaneously. For example, a developer will be able to work on the view while another one will be able to work on the controller at the same time. This completes the project quicker than expected.
With the MVC model, it is possible to build multiple views for a model. As here, business logic and data are separated from the display, and hence code duplication is very limited.
One can keep making frequent changes like for the fonts, screen layouts, colors, and adding new device support for tablets or mobile phones without influencing the model.
The MVC architecture returns the data using the same components with any interface.
MVC design pattern supports web applications or web pages that are SEO friendly. This way, the SEO friendly URLs can be used to generate more visits to the app or site.
Disadvantages of MVC Architecture:
- The framework navigation can be complex because it introduces new layers of abstraction and hence it can be hard to understand.
- Developers using MVC need to be skilled in multiple technologies to efficiently work with the complex framework.
Model View Presenter (MVP) Pattern
This came to the picture in early 2007 when Microsoft introduced the Windows Smart Client applications. When compared, the MVP pattern is very similar to the MVC pattern. It is derived from the MVC pattern, wherein the controller is replaced by the presenter. The MVP is an architectural pattern that can be used to bridge the gaps of some of the shortcomings of MVC.
The page controls are managed and displayed by View. The Presenter addresses UI events and collects all the input coming from the users and then moves it to the Model side, taking the result to the View.
It is from the logic end that the Presenter does all its work for gestures like directing through the navigation or pushing a button. When it comes to implementation, MVP is a compound pattern, but if you manage to apply it as an amazingly well-designed solution, it will offer you great benefits. In most of the cases, MVP is selected for ASP.NET Web Forms and Windows Forms applications. It can be used in web applications and so is the right choice for Android Developers.
This pattern divides an application into the Model, View, and Presenter.
The model continues to contain the data in a set of classes that describes the business logic and data. It also defines how the data can be changed and manipulated.
The view continues to implement the fragment classes but the area of what the view control changes. The View also initiates the user inputs, and delegates events to Presenter and the host processes and receives data from models. View directly interacts with users like XML, Activity, fragments. It does not contain any logic implemented.
The last part is the presenter, handling UI updates based on changes to the data model, and also processes user inputs. The Presenter receives the input from users via View, then processes the user’s data with the help of Model and passes the results back to the View. The Presenter communicates with view through the interface. The interface is defined in the presenter class, to which it passes the required data. In this MVP design pattern, the presenter overpowers the model and also updates the view. The View and Presenter are completely disconnected from each other and can only communicate through an interface. This makes unit testing of the applications much easier.
Advantages of MVP Architecture
It is easier to debug any applications as MVP introduces three different layers of abstractions. In MVP, developers are able to carry out unit testing while developing the application as the business logic is entirely separate from View.
In the case of MVP, one can have multiple presenters in order to control the Views. This way the codes can be reused in a better manner. Well, this is quite beneficial as one will not have the plans to have a single presenter just to control different Views.
MVP keeps the business logic and the persistence logic separate out of the Activity and Fragment classes. This enables the concerns are separated in a better way.
Disadvantages of MVP Architecture
- Higher unpredictability
- An additional expectation to absorb information
- Experience and information has any kind of effect in the correct usage
- Not reasonable for straightforward and little arrangements
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Model View View Model (MVVM) Pattern
It is the most well organized and most reusable way to organize the code. In MVVM pattern, we find two-way data binding between View and View-Model. The MVVM pattern organizes and structures the codes into maintainable and testable applications. This has the advantages of easier testing and modularity, while also reducing the amount of glue code that one has to write to connect the view + model. The Model-View-ViewModel (MVVM) pattern helps to cleanly segregate the business and presentation logic of any application from its user interface (UI). This helps to address a number of development issues that makes an application easier to test, maintain, and evolve. It also greatly improves code reuse opportunities and allows developers and UI designers to collaborate easily when developing their respective parts of an app.
We have three core components in the MVVM pattern: the model, the view, and the view model.
The model is the actual data and/or information that the developers and designers deal with. It is referred to as the domain object. An example of a model could be a contact or the characteristics of a live streaming publishing point. Model is something that holds the information, but not behaviors or services that manipulate the information. Model classes are usually used in conjunction with services that enclose data access and caching.
The view is only thing the end user actually interacts with. The view takes certain liberties to make the data more presentable. The view is active in MVVM in comparison to a passive view which has no idea of the model and is completely manipulated by a controller/presenter. The view in MVVM has behaviors, events, and data-bindings that ultimately require knowledge and idea of the underlying model and ViewModel. The view is not responsible for maintaining its state. Instead, it synchronizes with the ViewModel. A view also has behaviors associated with it, such as accepting user input.
The ViewModel is ideally a model for the View of the app. The ViewModel is a key component of the triad as it introduces Presentation Separation. It is the concept of keeping the nuances of the view separate from the model. Instead of making the Model informed about the user's view of date, it converts the date to the display format. It is responsible for coordinating the view's interactions with any model classes that are required. The properties and commands that the view model provides characterize the functionality to be offered by the UI.
Advantages of MVVM
With MVVN it is possible to reach out to the smaller parts of the codes and make changes accordingly due to the separation of different kinds of code in a cleaner manner. This accelerates the work and helps with new releases.
Writing unit tests against the core logic becomes easier as all the internal and external dependencies remain in the code containing the core logic of the application.
Designers and developers can work independently and simultaneously on their components during the development process. Designers can focus on the view, while developers can work on the view model and other components side by side.
The app UI can be redesigned without touching the code, but the view has to be implemented entirely in XAML. Hence, a new version of the view should work with the existing view model.
Disadvantages of MVVM
- Communication between various MVVM components and data binding can be exhausting.
- Code reusability of views and view model is difficult to achieve.
- Operating view models and their state in nested views and complex UI's is difficult.
- MVVM for beginners is difficult to put to use.
Conclusion on MVC vs MVP vs MVVM
Both MVP and MVVM are derived from MVC. The main difference between MVC and its derivatives is the dependency that each layer has on other layers, as well as how tightly bound they are to each other.
In MVC, the View sits on top of the architecture with the controller beside it. Models sit below the controller, so the Views know about the controllers and controllers get to know about the Models. Here, the Views have direct access to Models. Exposing the complete Model to the View might have security and performance issues, depending on the complexity of our application.
In MVP, the controller is replaced by the Presenter. Presenters sit at the same level as views, listening to events from the View and model, and connecting the actions between them. Since there isn’t a system for binding Views to ViewModels, it depends on each View implementing an interface allowing the presenter to interact with the View.
MVVM, however, allows to create View-specific offshoots of a Model, containing state and logic information, avoiding the need to expose the entire Model to a View. The ViewModel is not required to reference a View contrary to the MVP’s Presenter. The View can bind to properties on the ViewModel, which exposes the data contained in Models to the View.
However, a level of interpretation is needed between the ViewModel and the View, and this can have performance costs. The complexity of this interpretation also varies from copying data to manipulating it to a form we would like the View to see. MVC doesn’t have this issue, because the whole Model is readily available and such manipulation is easy to avoid.
|Controller is the entry point to the Application||View is the entry point to the Application||View is the entry point to the Application|
|One to many relationships between Controller & View||One to One mapping between View & Presenter||One to many relationships between View & View Model|
|View Does not have reference to the Controller||View have references to the Presenter||View have references to the View-Model|
|View is aware of the Model||View is not aware of the Model||View is aware of the Model|
|Smalltalk, ASP.Net, MVC||Windows forms||Silverlight, WPF, HTML5, with AngularJS|
|MVC is Old Model||MVP (more modular because of its low-coupling. Presenter is a mediator between View and Model)||MVVM (Two-way binding between VM and UI component, more automated than MVP)|