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Many Lints

prefer_bloc_extensions

v0.4.0 Warning Fix Bloc / Riverpod

This rule flags BlocProvider.of<T>(context) and RepositoryProvider.of<T>(context), and offers a quick fix rewriting them to context.read<T>(). When listen: true is passed, the fix produces context.watch<T>() instead.

Why use this rule

Section titled “Why use this rule”

BlocProvider.of and the extensions do the same lookup, but the extension puts the subscription decision in the method name. With of, whether the widget rebuilds on state changes depends on a listen: argument that is easy to omit and easy to misread — and its default (false) is silent, so a widget that should rebuild simply never does.

See also: BlocProvider | context.read vs context.watch

Examples

Section titled “Examples”

Dispatching an event

Section titled “Dispatching an event”

A one-off read in a callback becomes context.read:

// Don't
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


sealed class CounterEvent {}


class Increment extends CounterEvent {}


class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0);
}


void onTap(BuildContext context) {
  BlocProvider.of<CounterBloc>(context).add(Increment());   // LINT
}
// Do
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


sealed class CounterEvent {}


class Increment extends CounterEvent {}


class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0);
}


void onTap(BuildContext context) {
  context.read<CounterBloc>().add(Increment());
}

listen: true becomes watch

Section titled “listen: true becomes watch”

Reading state in build needs a subscription, so the fix produces watch:

// Don't
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


class CounterCubit extends Cubit<int> {
  CounterCubit() : super(0);
}


Widget build(BuildContext context) {
  final count = BlocProvider.of<CounterCubit>(context, listen: true).state; // LINT
  return Text('$count');
}
// Do
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


class CounterCubit extends Cubit<int> {
  CounterCubit() : super(0);
}


Widget build(BuildContext context) {
  final count = context.watch<CounterCubit>().state;
  return Text('$count');
}

Repositories too

Section titled “Repositories too”

RepositoryProvider.of is reported on the same terms:

// Don't
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


class UserRepository {}


void load(BuildContext context) {
  final repo = RepositoryProvider.of<UserRepository>(context);   // LINT
}
// Do
import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';


class UserRepository {}


void load(BuildContext context) {
  final repo = context.read<UserRepository>();
}

Known limitations

Section titled “Known limitations”

Only BlocProvider and RepositoryProvider resolving to package:flutter_bloc, package:bloc or package:provider are matched. A project’s own wrapper with an of static is not reported.

A dynamic listen: argument (listen: shouldWatch) is treated as false, since the rule can only read a boolean literal — so the fix would produce read where watch may be wanted.

Configuration

Section titled “Configuration”

This rule is in the opinionated preset, so it is on with preset: opinionated, or by name:

many_lints.yaml
rules:
  prefer_bloc_extensions: true

To turn it off again:

many_lints.yaml
rules:
  prefer_bloc_extensions: false

To keep the rule on but skip certain paths, use per-rule exclude.

Section titled “Related rules”