Saving Data on Android

INSERT INTO
 query using the object that you 
received as a parameter to create a new record.
3. The 
@Query
 annotation executes the query passed as a parameter. In this case, 
you are performing a delete operation by executing a 
DELETE FROM
 query.
4. This is another 
@Query
 annotated method that retrieves all the questions from 
your database.
Don't worry if something does not make sense right now. You will be learning much 
more about DAOs in the 
The DAO Pattern
 chapter.
Repository
This class acts as a bridge between your data sources and your app. The repository 
class handles the interaction with your Room database and other backend endpoints 
such as web services and Open APIs.
Saving Data on Android
Chapter 5: Room Architecture
raywenderlich.com
98

---

ViewModel
Just like the 
Repository
 acts as a bridge between your data sources and your app, 
the 
ViewModels
 act as a bridge between your repository and your user interface. The 
ViewModel
 communicates the data coming from your 
Repository
 to your Views and 
has the advantage of surviving configuration changes since it's lifecycle-aware.
LiveData
LiveData
 is a data holder class that implements the 
Observer
 pattern. This means it 
can hold information and be observed for changes. Your views such as 
Fragments
 or 
Activities
 observe 
LiveData
 objects returned from your 
ViewModels
 and update 
the relevant widgets as needed.
The interaction between the above components can be illustrated by the following 
diagram:
You will be learning much more about the above components in the upcoming 
chapters, , this is all you need to know.
Saving Data on Android
Chapter 5: Room Architecture
raywenderlich.com
99

---