What is this repository for :question:

Simple Application with one to one connectivity using Firebase Real time Database written in MVC,MVP and MVVM architecture to better understand the android coding patterns. Purpose of writing same application functionality with 3 different pattern is to show how single application can be developed using 3 different patterns(Mvc, Mvp, Mvvm) :relieved:.

Mvc (Model View Controller) :part_alternation_mark: :heavy_check_mark: C

Mvc is a clean approach in android putting views away from the controller. the controller is only responsible for updating models, once the model gets updated it can notify views and then the view can be updated using proper callbacks. Traditional MVC is where there is a

Model : Acts as the model for data
View : Deals with the view to the user which can be the UI
Controller :Controls the interaction between Model and View, where view calls the controller to update the model. A view can call multiple controllers if needed..

Mvp (Model View Presenter) :part_alternation_mark: :heavy_check_mark: :parking:

Some disadvantages of MVC can be overcome using Mvp approach. Presenter in Mvp contains all business logic and this class is far away from android Context or android related dependencies which provides flexibility to text business logic by simply using presenter class in test modules. Android related dependencies create complexity in testing. The presenter does not have any android dependency like Context, View etc and all the model updates and network requests are done via presenter. Once the model gets updated or a network request completes, the view is updated via presenter using callbacks to view from the presenter. No model and network request can directly approach views.

Mvvm (Model View View-Model) :part_alternation_mark: :heavy_check_mark: :heavy_check_mark: :part_alternation_mark:

MVVM involves a data binding approach to make code short and reduce view handling code from java classes. View models are responsible to update view and once a view model is tied to a view then view get notified about their updating events. If a model gets updated by a user click then model send callbacks to view model which updates the view automatically as it gets tied to the views. Mvvm reduce code size but the implementation of MVVM is quite tough and it is difficult to debug big projects based on Mvvm.

Choice of correct architect

:eyes:
Choice of a correct architecture for the project involves the understanding of the modules which needs to be developed. Some functionalities works great on MVC, some with Mvp and some with Mvvm. It is quite difficult to debug the projects made on MVVM specially those which doesn't have one sided data flow due to data binding and live data. If an application receives a continuous data stream from a source, needs a regular UI-update and has majorly(80–90%) one sided communication(eg: an electronic devices sending logs to a android app) like solar-cell apps, inverters apps, or any other device's status monitoring can work well with MVVM due to live data - UI update. Debugging these MVVM applications can be easy as major flow of data is one sided.

MVP is a good approach for writing android projects when we are concerned about testing the business logic w.r.t unit testing via JAVA test frameworks(Not Android). Since JAVA test framework will only resolve java dependencies and a clean presenter layer is free from android related dependencies like context, sharedpreferences, or any other com.android.* package. Drawback of MVP is that it ends up writing 20-25% extra code with the same functionality written in MVC or MVVM. Mvp is good if you are really interested in test cases and unit testing of modules. For MVP using java test kits just make instance of presenter and run test functions.

eg: new Presenter().testSomeFunction().

Mvc is widely used technique in android. Google itself wrote it's repositories in MVC for many years. Now a days google is adopting MVVM for it's github repositories as these repo's are small and majorly samples. MVC application can be tested via android test frameworks not with JAVA specific test tools due to lack of dependencies of com.android.* packages in java specific tool.

Example:

1. A chat application can be writtten in MVC, MVP, MVVM depending on testing requirements and flow of data.
2. A luminous inverter monitoring application can work best with MVVM due to major one sided data flow.
3. E-commerce application can be build in MVC, MVP but MVVM may make some modules very complex.

NOTE: There is no single architecture which is best of all. If there was one, there wouldn't be any need of learning other architectures. Choice of correct architecture depends on several factors like initial requirements, data flow, scalability, maintenance, updates(CRs), testing requirements.

Except these three android architectures, there is one more architecture named as "MVI - Model view Intent". This is not very popular among Android developers. Please check this link if you are interested in MVI.
https://github.com/saksham24/Android-simple-MVI-pattern-with-MVP-MVVM-collaboration

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