The Model View Controller is an architectural pattern that makes it easy to develop applications that are easy to develop, test, and maintain.
The Model View Presenter design pattern replaces the controller with the presenter, which manipulates the model when the view is updated. The presenter contains business logic in the MVVM design pattern while the view and model are isolated.
This article is about the MVC, MVP, and MVVM patterns.
History of the Model-View-Controller
It was in 1979 when the computer scientist Trygve Mikkjel Heyerdahl Reenskaug denied MVC design. He was looking for a way to break a large user application down into smaller, more manageable components.
The MVC pattern was originally used in the small talk programming language. Model-View-Editor was one of the original names for the pattern, but it was changed to Model-View-Controller. The MVC pattern was widely used in desktop applications in the 1980s and early 1990s. It became widespread in the late 1990s.
Read: Explore REST APIs with Spring MVC
Architectural patterns vs. design patterns
An architecture pattern is a generic, reusable solution to a recurring problem in software architecture in a specific context. Architectural patterns address a variety of software development challenges, such as: B. Performance limitations of the computer hardware, high availability and reduction of business risk. Some common architectural patterns include model-view-controller patterns, model-view-view-model, client-server patterns, shift patterns, and so on.
Design pattern are recommended solutions and procedures for common problems in software applications. While an architectural pattern is about the overall structure of the application, a design pattern is about how a component should be built in the application.
Architectural patterns deal with how the major components of the system work together, how messages and data flow through the system, and other structural considerations. Architectural patterns use several types of components, each of which is often made up of smaller modules.
Read: Use of design patterns for productivity
The Model View Controller (MVC) pattern
The Model View Controller (MVC), an architecture pattern, decouples the presentation and business logic layers of an application. It contains three components: the model, the view, and the controller. The model represents the application’s data, the view displays data, and the controller updates the view when the data changes.
The model has no understanding of the view or the controller. Usually it warns its watchers if there is a change.
The main goal of the MVC pattern is to separate concerns to facilitate testability. The MVC pattern allows you to separate the problems while making it easier to test and maintain your application code.
In a typical MVC architecture, the request is routed via the controller and connects the model with the corresponding view. The MVC pattern is a composite pattern because while the view and controller use the strategy design pattern, the view and model are synchronized using the observer design pattern. The view subscribes to model changes. Since the view and controller are decoupled, a controller can be used with several views in the MVC pattern.
The advantages of the MVC pattern are:
- Clear separation of concerns
- Makes it easy to test your application code
- Accelerated parallel development
- Promotes the decoupling of the application layers
- Allows for better code organization, extensibility, and reuse
Despite the advantages, the MVC pattern also has some disadvantages:
- It’s pretty complex to implement
- It is not a good choice for small applications
Components of the MVC pattern
The components of the MVC pattern are as follows.
model
The model stores data and communicates directly with the database. All data and the associated logic for the application are stored here. It is responsible for defining business rules that regulate the handling of data and the modification or processing of data. The model does not know the controller and the view and usually notifies its observers of any changes in the model.
view
The view displays the model’s data and is responsible for how the data is presented in the user interface and how end users interact with the application. The view is the visual representation of the model data displayed in grids, tables, charts, graphs, forms, and other similar elements.
Regulator
The controller controls how a user interacts in MVC applications. Controllers handle incoming requests and handle user interactions and input. They also execute the appropriate application logic. In other words, the controller receives the input from the user, reviews the input data, and then executes the appropriate business logic that changes the state of the data model.
The Model View Presenter (MVP) pattern
As with the MVC pattern, there are three components to the MVP pattern. These are the model, the view, and the presenter. The presenter replaces the controller (in MVC) in the MVP design pattern. The MVP pattern makes it easier to mimic the view and unit test applications more efficiently. In the MVP pattern, the presenter manipulates the model while simultaneously updating the view.
If your application needs to support multiple user interface technologies, the MVP design pattern is better than the MVC pattern. It’s also a great choice if your user interface is complicated and requires a lot of user interaction. The MVP design pattern is better suited for automated unit testing of your app’s user interface than the traditional MVC design.
Read: Introduction to software design patterns with Java
Variations on the MVP design pattern
The MVP design pattern has two variations:
- Passive View – With this strategy, the view does not recognize the model and is updated by the presenter.
- Supervising Controller – In this strategy, the view interacts directly with the model to bind data to data controls. The presenter updates the model and manipulates the view only when necessary.
The MVP design pattern has the following advantages:
- Clear separation of concerns
- Modularity
- Code easier to test
The Model View – View Model (MVVM) pattern
The ModelView-ViewModel (MVVM) design pattern is a variation of Martin Fowler’s Presentation Model Design Paradigm, which is based on the popular MVC pattern. The ViewModel helps to separate the presentation layer. The presenter contains the business logic in the MVVM design pattern, and the view is isolated from the model.
The view component recognizes the presenter even if the presenter does not see the view. The presenter represents an abstract view of the user interface. A passive view has no understanding of the model. The view is active in the MVVM design pattern and contains actions, events, and data binding information.
Note that the view in MVVM does not maintain status information. instead it is synchronized with the ViewModel. In MVVM, the ViewModel isolates the presentation layer and provides methods and commands for managing the state of a view and for manipulating the model.
The view and view model in the MVVM design pattern communicate using methods, properties, and events. The view and the view model have a two-way data binding or two-way data binding that guarantees that the models and properties of the view model are synchronized with the view. In applications that require two-way data binding, the MVVM design pattern is ideal.
The MVVM design pattern has the following advantages:
- Better separation of concerns
- Code reuse
- Easier to test and maintain
Summary of design patterns for software development
A good understanding of the MVC, MVP, and MVVM patterns can help you create applications that are extensible, maintainable, and reusable. This article provides a head start on the MVC, MVP, and MVVM patterns and their pros and cons.
