Avoid Public Fields

newdartrecommended

Avoid exposing public fields on Bloc and Cubit instances.

Rationale

Business logic components maintain their own state and emit state changes via the emit API. As a result, all public facing state should be exposed via the state object.

Examples

DO NOT expose public fields on bloc and cubit instances.

BAD:

counter_bloc.dart

import 'package:bloc/bloc.dart';

enum CounterEvent { increment };

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterEvent>((event, emit) => emit(state + 1));
  }

  // Avoid public fields!
  // Prefer to keep all external state in the [state] object.
  int count = 0;
}

GOOD:

counter_bloc.dart

import 'package:bloc/bloc.dart';

enum CounterEvent { increment };

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterEvent>((event, emit) => emit(state + 1));
  }
}

Enable

To enable the avoid_public_fields rule, add it to your analysis_options.yaml under bloc > rules:

YAML List

analysis_options.yaml

bloc:
  rules:
    - avoid_public_fields

YAML Map

analysis_options.yaml

bloc:
  rules:
    avoid_public_fields: true