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[WIP] BlocProvider w/multiple Blocs
import 'package:flutter/material.dart';
import 'package:bloc/bloc.dart';
/// A Flutter widget which provides a bloc to its children via `BlocProvider.of(context)`.
/// It is used as a DI widget so that a single instance of a bloc can be provided
/// to multiple widgets within a subtree.
class BlocProvider extends StatefulWidget {
/// The Blocs which are to be made available throughout the subtree.
/// If multiple blocs are provided, the blocs will be inserted in the same order they are specified.
/// For example if blocs: [BlocA, BlocB] BlocA will the an ancestor of BlocB.
/// Blocs must not be null or empty.
final List<Bloc> blocs;
/// The Widget and its descendants which will have access to the Bloc.
/// This must not be null.
final Widget child;
BlocProvider({
Key key,
@required this.blocs,
@required this.child,
}) : assert(blocs != null && blocs.isNotEmpty),
assert(child != null),
super(key: key);
@override
_BlocProviderState createState() => _BlocProviderState();
/// Method that allows widgets to access the bloc as long as their `BuildContext`
/// contains a `BlocProvider` instance.
static B of<B extends Bloc<dynamic, dynamic>>(BuildContext context) {
final type = _typeOf<_BlocProviderInherited<B>>();
print('of $type');
final _BlocProviderInherited<B> provider =
context.ancestorInheritedElementForWidgetOfExactType(type)?.widget;
if (provider == null) {
throw FlutterError(
'BlocProvider.of() called with a context that does not contain a Bloc of type $B.\n'
'No ancestor could be found starting from the context that was passed '
'to BlocProvider.of<$B>(). This can happen '
'if the context you use comes from a widget above the BlocProvider.\n'
'The context used was:\n'
' $context');
}
return provider?.bloc;
}
static Type _typeOf<B>() => B;
}
class _BlocProviderState extends State<BlocProvider> {
@override
Widget build(BuildContext context) =>
_buildBlocProviders(widget.blocs, widget.child);
Widget _buildBlocProviders(List<Bloc> blocs, Widget child) {
return blocs.length == 1
? _BlocProviderInherited(
bloc: blocs.first,
child: child,
)
: _BlocProviderInherited(
bloc: blocs.removeAt(0),
child: _buildBlocProviders(blocs, child),
);
}
}
class _BlocProviderInherited<B extends Bloc<dynamic, dynamic>>
extends InheritedWidget {
_BlocProviderInherited({
Key key,
@required Widget child,
@required this.bloc,
}) : super(key: key, child: child) {
print('building ${_typeOf<B>()}');
}
final B bloc;
static Type _typeOf<B>() => B;
@override
bool updateShouldNotify(_BlocProviderInherited oldWidget) => false;
}
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