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MVC: At Its Core

Designing an application requires a lot of effort And without a proper structure there are chances that your application may fail during some operations. That is the reason of choosing a framework to accomplish the task of building an application. A framework enforces you to use the defined application structure and methods so that you can easily maintain your code and refactor it if needed. MVC , short form for Model View Controller is a designing pattern in which an application is divided into 3 components i.e. Models, Views and Controllers. (The word Application infers to all type of applications like mobile apps, desktop apps, web apps etc.). A framework which follows the MVC pattern is known as a MVC framework and there are a lot of frameworks for each type of application written in most of the languages. Normally people start learning about the framework without understanding the concept behind them. Each MVC framework follows the same pattern i.e. the MVC pattern. So if we learn about MVC then we can pick any framework of our choice and it'll take lesser time to understand their API. So in this article, we'll focus on MVC pattern rather than the framework. These are things we'll be learning today.

MVC Components

As i mentioned earlier, using MVC pattern means that you'll have to break your application in 3 components. You'll be wondering why that is even necessary ? The reasons are many but to list a few, it helps you write maintainable code by structuring your code in different modules, easily testable, easily scalable, easy to understand by others and list is going.. Still if you don't understand the importance of MVC then lets check out the components and then you'll be able to visualise the modularity. The components of a MVC based application are modals, views and controllers.

  • Modals :

    This is the component which is responsible to modify the data stored by your application. The data can be stored anywhere like in a database, in a file, in dynamic arrays etc. This component provides a handy API which can be used by other parts of your application to send data to database, retrieve data from database etc. The data definition (eg. database schema) and the data store (eg. MYSQL connections) connections are also managed by the Modal component. You just tell modal what to store and it takes care of the rest of the details like where, when, how to store.

  • Views :

    This is the component which displays the data. It does nothing else but only displays the data. You must be thinking that why we need a component for displaying the data if we can simply output it ? Actually a view is a reusable fragment of code so you can use a same view to diaplay 2 different types of data. For example, you might need to show price of an item in rupees if user is indian and in dollars if he is american (Its just an example. I obviously know that rupees and dollars are currencies of many more countries.) So instead of returning the value and the sign wrapped in a label widget(GUI apps) or in HTML tags(web apps), you can simply create a view which shows a value and a sign and you can pass your data to it.

  • Controllers :

    Controllers are the machinery which actually runs your application. It forms a bridge between the views and the modals. Controllers are the ones which asks the modals for some data, performs some operations on it and then send them to views. In a non-mvc application, what most people do is either they put all of their code in controllers or use any 1 more component along with controller like MC or VC. Thats when applications start to become unstable.

MVC Flow

The flow of an MVC application is really important for us to understand. We already know about the components so now lets see how they work so that we can visualise what exactly is going on. Below is a simple block diagram describing the placement of the components.

The main thing of your application is the routes using which a user can access your application views. From the perspective of a web app, a route is the url which user clicks and a controller will be called to perform an action. Consider a route to be a trigger to call a controller for handling. In web apps, triggers are urls and in mobile/desktop apps, triggers are buttons or actions (swipe). So routes are defined to trigger the controllers. Lets see the ongoing process when a user logs into an app.

  1. Lets suppose user just opens your app (may be url :'/home' or just click app icon).
  2. A controller is called to display the login form. That controller does nothing but returns a view containg a login form.
  3. The returned view displays the login form to the user.
  4. User fills out the form and clicks the signin button (trigger)
  5. A different controller is called which recieves the data. It queries the modal to check for the existence of the user with the given credentials.
  6. Modal checks for the user's existence and returns result to the controller.
  7. Controller checks the result. If user exists then it return dashboard view otherwise it returns the login view again

Popular MVC Frameworks

The work flow of a login process which we saw earlier is a very basic one. There are a lot of things which frameworks handle for us like session management, request/responses, cache, cookies, database connections, security, form handling etc. So instead of building an application from the scratch without a framework, we should use frameworks for performance and reliability. There are hundreds of frameworks avaiable in the market for different languages and for different purposes. I'll list a few here but you are welcome to suggest any popular framework which is missing.

Framework Language Type
Express Javascript Web
Django Python Web
Laravel PHP Web
Angular Javascript Web
ASP.NET C#/VB Mobile/Web
Ruby on Rails Ruby Web
Spring Java Any
Ionic Web languages Hybrid mobile
Catalyst Perl Web
Phonegap Web languages Hybrid mobile

These are a lot more frameworks other than the above listed. But these are the ones which are widely used. If you want to share some more frameworks then you can write them in comments. Also it would be nice if you take a moment in sharing the article if you learnt something. Happy coding.

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Comments

  1. Tejuteju4 September 2018 at 21:54

    It was really a nice post and i was really impressed by reading this Ruby on Rails Online course

    ReplyDelete

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