In our previous blog post we have learnt about Agera, about Reactive programming and Sample code of Hello World Example using Agera - Functional Reactive Programming for Android recommended by Google. In Hello World Example learn about Observable, Updatable, Supplier and Receiver
In this blog I am going to introduce Repository.
What is the Repository ??
The most important concept in Agera is the Repository. Repositories receive, supply, and store data and emit updates. The interfaces Observable, Supplier and Receiver are combined into two types of repositories:
| Interface | Observable | Supplier | Receiver |
Repository | ☑ | ☑ | ☐ |
MutableRepository | ☑ | ☑ | ☑ |
In our hello world code, you could replace
implements Observable, Supplier<String>, Receiver<String>
with
implements MutableRepository<String>
but Agera provides a Repository factory, so remove the
MyDataSupplier class altogether and replace MyDataSupplier myDataSupplier = new MyDataSupplier();
with
MutableRepository<String> mStringRepo = Repositories.mutableRepository("Initial value by Agera with Repository");
mutableRepository() creates a repository similar to our previous implementation, but that is thread-safe and has a more sophisticated update dispatcher, so let's use that from now on.
Also, remove the
updatables (with removeUpdatable()) when you know you're done with them. In our example this is not needed but it is a good practice: it avoids potential leaks and prevents updating destroyed views. The class is now much shorter: public class JavaMainActivity extends AppCompatActivity {
// MyDataSupplier myDataSupplier = new MyDataSupplier();
// Updatable updatable;
private MutableRepository<String> mStringRepo;
private Updatable mLoggerUpdatable;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mStringRepo = Repositories.mutableRepository("Initial value by Agera with Repository");
final TextView textView = findViewById(R.id.textView);
// Create an Updatable
// updatable = new Updatable() {
// @Override
// public void update() {
// Log.d("AGERA", myDataSupplier.get());
// textView.setText(myDataSupplier.get());
// }
// };
// myDataSupplier.addUpdatable(updatable);
// myDataSupplier.accept("Hello Agera!");
// Create an Updatable by Respository
mLoggerUpdatable = () -> {
Log.d("AGERA", mStringRepo.get());
textView.setText(mStringRepo.get());
};
}
@Override
protected void onStart() {
super.onStart();
mStringRepo.addUpdatable(mLoggerUpdatable);
// Change the repository's value
mStringRepo.accept("Hello World by Agera with Repository");
}
@Override
protected void onStop() {
mStringRepo.removeUpdatable(mLoggerUpdatable);
super.onStop();
}
}In summary:
Agera uses very simple interfaces you should be aware of:
Observable, Updatable, Supplier and Receiver. These are combined in the Repository and MutableRepository interfaces.- Agera provides a factory of implementations of these simple Repositories:
Repositories.mutableRepository(T)andRepositories.repository(T)for immutable repositories.
