What is MVVM Architecture ?
MVVM (Model-View- ViewModel) is industry- recommended architecture that removes the tight coupling among components in an application. Most notably, this architecture only references the parent through observables, rather than giving the children direct access to it.
Model
This is a business object that encapsulates the data and behavior of the application domain. To get and save the data in your application, this Model and the ViewModel will work together.
View
It defines the structure, layout, and appearance of the users's action on the screen. Through data binding (properties, event callbacks) it forwards the user's interaction to view model.
ViewModel
This model is specifically designed for the View to get data from the Model passed to it with logic. It acts as a link between the Model and the View to implement specific logic in your applications.
Features
• The application's lifecycle state will be preserved. • The user's last position in the application will be retained. • Business logic is kept separate from UI components. • Operations on the database are kept separate from the business logic. • It’s simple to read and understand.
Workflow
ViewModel reads model objects from the server and then supports the simple presentation of data on the View using Get Data (available in model objects).
Implementation
In Android projects, the MVVM design pattern can be applied: • Using the Google’s DataBinding library. • Using another data binding tool, such as RxJava.
Advantages
• Increase the code reusability. • For maintenance, it can stay flexible and swiftly release new versions. • It is extensible, letting you add new code or replace existing code. • When all modules are independent, it is easier for developers to write unit tests against core logics.
Disadvantages
• For smaller projects, this design pattern doesn’t work well. • Application debugging will be a little more difficult if the data-binding logic is incredibly complex. • The ViewModel’s design can be complicated in more complex situations.