BlocLifecycle

bloc_lifecycle.dart

import 'package:auto_route/auto_route.dart';
import 'package:bloc/bloc.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

extension BlocLifecycleEx on BuildContext {
  T bloc<T extends Cubit<Object>>() => BlocLifecycle.of<T>(this);
}

/// Callback when BLoC ready to create
/// [bloc] - previous closed BLoC or null if first create
typedef BlocLifecycleCreate<T> = T Function(
  BuildContext context,
  T bloc,
);

/// Callback when BLoC ready to close
typedef BlocLifecycleClose<T> = void Function(
  BuildContext context,
  T bloc,
);

/// Widget is responsible for the life cycle of the block, rebuilding when context is changed.
@immutable
class BlocLifecycle<T extends Cubit<Object>> extends StatefulWidget {
  final Widget child;
  final BlocLifecycleCreate<T> create;
  final BlocLifecycleClose<T> close;
  const BlocLifecycle({
    @required this.child,
    @required this.create,
    this.close,
    Key key,
  })  : assert(child != null, 'Field child in widget BlocLifecycle<T> must not be null'),
        assert(create != null, 'Field create in widget BlocLifecycle<T> must not be null'),
        super(key: key);

  static T of<T extends Cubit<Object>>(BuildContext context) => _BlocLifecycleStateScope.of<T>(context)?.bloc;

  @override
  State<BlocLifecycle<T>> createState() => _BlocLifecycleState<T>();
}

class _BlocLifecycleState<T extends Cubit<Object>> extends State<BlocLifecycle<T>> {
  T bloc;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _closeIfNotNull();
    bloc = widget.create(
      context,
      bloc,
    );
  }

  @override
  void dispose() {
    _closeIfNotNull();
    bloc = null;
    super.dispose();
  }

  void _closeIfNotNull() {
    if (bloc != null) {
      if (widget.close != null) {
        widget.close(
          context,
          bloc,
        );
      }
      bloc.close();
    }
  }

  @override
  Widget build(BuildContext context) => _BlocLifecycleStateScope<T>(
        bloc: bloc,
        child: widget.child,
      );
}

@immutable
class _BlocLifecycleStateScope<T extends Cubit<Object>> extends InheritedWidget {
  final T bloc;

  const _BlocLifecycleStateScope({
    @required Widget child,
    @required this.bloc,
    Key key,
  })  : assert(child != null, 'Field child in widget _BlocLifecycleState must not be null'),
        assert(bloc != null, 'Bloc must not be null'),
        super(key: key, child: child);

  /// Find _BlocLifecycleStateScope in BuildContext
  static _BlocLifecycleStateScope of<T extends Cubit<Object>>(BuildContext context) =>
      context.dependOnInheritedWidgetOfExactType<_BlocLifecycleStateScope<T>>();

  @override
  bool updateShouldNotify(_BlocLifecycleStateScope oldWidget) => !identical(bloc, oldWidget.bloc) || bloc != oldWidget.bloc;
}