MVC, MVP, and MVVM are three popular design patterns in software development. Let’s have a look on Model View Controller (MVC), Model View Presenter (MVP) and Model View View-model (MVVM) one by one. All these design patterns by and large help in developing applications that are loosely combined, easy to test and maintain. All discussion about the pattern is made in context of Android as a platform.
MVC design pattern divides an
application into three major aspects: Model, View, and Controller.
Model
Model means data that is
required to display in the view. Model represents a collection of classes that
describes the business logic (business model and the data model). It also
defines the business rules for data means as how the data can be changed and
manipulated.
View
The View represents UI
components like XML, HTML etc. View displays the data that is received from the
controller as the outcome. In MVC pattern View monitors the model for any state
change and displays updated model. Model and View interact with each other
using the Observer pattern.
Controller
The Controller is responsible
to process incoming requests. It processes the user’s data through the Model
and passing back the results to View. It normally acts as a mediator between
the View and the Model.
Model View Presenter (MVP)
The MVP pattern is similar to
the MVC pattern. It is derived from MVC pattern, wherein the controller is
replaced by the presenter. This pattern divides an application into three major
aspects: Model, View, and Presenter.
Model
The Model represents a set of
classes that describes the business logic and data. It also defines business
rules for data means how the data can be changed and manipulated.
View
View is a component which is
directly interacts with user like XML, Activity, fragments. It does not contain
any logic implemented.
Presenter
The Presenter receives the
input from users via View, then process the user’s data with the help of Model
and passing the results back to the View. Presenter communicates with view
through interface. Interface is defined in presenter class, to which it pass
the required data. Activity/fragment or any other view component implement this
interface and renders the data in a way they want.
In the MVP design pattern, the
presenter manipulates the model and also updates the view. In MVP View and
Presenter are completely decoupled from each other’s and communicate to each
other’s by an interface. Because if decoupling mocking of the view is easier
and unit testing of applications that leverage the MVP design pattern over the
MVC design pattern are much easier.
Model View View-model (MVVM)
MVVM pattern supports two-way
data binding between View and View-Model. This allows automatic propagation of
changes, inside the state of View-Model to the View. Generally, the View-Model
utilizes the observer pattern to inform changes in the View-Model to the Model.
View-Model
It is
responsible for exposing methods, commands, and other properties that help to
maintain the state of the view, manipulate the model as the result of actions
on the view, and trigger events in the view itself. View has a reference to
View-Model but View-Model has no information about the View. There is
many-to-one relationship between View and View-Model means many Views can be
mapped to one View-Model. It is completely independent of Views.
The
bi-directional data binding or the two way data binding between the view and
the View-Model ensures that the models and properties in the View-Model is in
sync with the view. The MVVM design pattern is well suited in applications that
need support for bi-directional data binding.
