bloc_state_gen

https://github.com/user-attachments/assets/97d02d6d-98af-415f-8538-ef432f4c2ed1

A lightweight Dart package that generates convenient extensions for BLoC state classes, offering pattern matching and logging capabilities through simple annotations.

Features

🎯 Pattern Matching

• match: Complete state pattern matching requiring all cases to be handled
• matchSome: Partial pattern matching with default case handling
• Compile-time type safety

📝 Logging

• Built-in state logging functionality
• Debug-friendly state information

Installation

1. Add bloc_state_gen to your pubspec.yaml:

   dependencies:
     bloc_state_gen: ^latest_version
   
   dev_dependencies:
     build_runner: ^latest_version
   

2. Update your main cubit class to include the generated file:

   import 'package:flutter_bloc/flutter_bloc.dart';
   import 'package:bloc_state_gen/bloc_state_gen.dart';
   
   part 'search_state.dart';
   part 'search_state.g.dart';
   
   class SearchCubit extends Cubit<SearchState> {
     SearchCubit() : super(const SearchInitial());
   }
   

3. Run the code generator:

   flutter pub run build_runner build
   

4. Ignore generated .g.dart files in version control by adding the following to your .gitignore:

   # Ignore generated files
   *.g.dart
   

Usage

Basic Setup

1. Annotate your state class with @BlocStateGen:

   part of 'search_cubit.dart';
   
   @BlocStateGen()
   abstract class SearchState {
     const SearchState();
   }
   
   class SearchInitial extends SearchState {
     const SearchInitial();
   }
   
   class Searching extends SearchState {
     final String query;
   
     const Searching({
       required this.query,
     });
   }
   
   class SearchResults extends SearchState {
     final String query;
     final List<String> results;
   
     const SearchResults({
       required this.query,
       required this.results,
     });
   }
   
   class NoResults extends SearchState {
     final String query;
   
     const NoResults({
       required this.query,
     });
   }
   
   class SearchError extends SearchState {
     final String message;
     final String? query;
   
     const SearchError({
       required this.message,
       this.query,
     });
   }
   

2. Run the code generator:

   flutter pub run build_runner build
   

Feature Usage

1. match - Complete Pattern Matching

Requires handling all possible states:

Widget buildStateWidget(SearchState state) {
  return state.match(
    searchInitial: () => const StartSearch(),
    searching: (query) => const CircularProgressIndicator(),
    searchResults: (query, results) => DisplayList(items: results),
    noResults: (query) => NoResultsWidget(query: query),
    searchError: (message, query) => ErrorMessage(message: message),
  );
}

2. matchSome - Partial Pattern Matching

Handle specific states with a default case:

String getDisplayText(SearchState state) {
  return state.matchSome(
    searchResults: (query, results) => 'Found ${results.length} results for: $query',
    searchError: (message, query) => 'Error${query != null ? " for $query" : ""}: $message',
    orElse: () => 'Idle...',
  );
}

3. log - State Logging

Print state information for debugging:

void debugState(CounterState state) {
  print(state.log());  // Outputs formatted state information
}

Customizing Generation

You can selectively enable/disable features using the @BlocStateGen annotation:

@BlocStateGen(
  match: true,      // Enable complete pattern matching
  matchSome: true,  // Enable partial pattern matching
  log: true,        // Enable logging functionality
)
abstract class SearchState {
  const SearchState();
}

Best Practices

1. Complete Pattern Matching

   • Use match when you need to handle all possible states
   • Ensures no state is accidentally forgotten
   • Provides compile-time safety

2. Partial Pattern Matching

   • Use matchSome when you only need to handle specific states
   • Always provide a meaningful orElse case
   • Useful for selective state handling

3. Logging

   • Enable logging during development for better debugging
   • Use in conjunction with Flutter's debug mode:

if (kDebugMode) {
  print(state.log());
}

Example Project

For a complete working example, check out our example project demonstrating:

• State class definition
• Extension generation
• Usage of all three core features
• Integration with Flutter UI

License

This project is licensed under the MIT License - see the LICENSE file for details.

Libraries

bloc_state_gen

builder