build abstract method
Initialize an AsyncNotifier.
It is safe to use Ref.watch or Ref.listen inside this method.
If a dependency of this AsyncNotifier (when using Ref.watch) changes, then build will be re-executed. On the other hand, the AsyncNotifier will not be recreated. Its instance will be preserved between executions of build.
If this method throws or returns a future that fails, the error will be caught and an AsyncError will be emitted.
Implementation
@visibleForOverriding
Stream<State> build();