Flutter SDK (FFI)

The Flutter SDK uses Dart FFI to call into the Rust evaluation core compiled as a native shared library. Evaluation is synchronous and happens on the Dart side with zero async overhead.

Installation

Add to your pubspec.yaml:

dependencies:
  sidekick_flutter: ^0.1.0

Then run:

flutter pub get

Quick Start

import 'package:sidekick_flutter/sidekick_flutter.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  final flags = SidekickClient(
    serverUrl: 'https://flags.yourcompany.com',
    sdkKey: 'your-sdk-key',
  );

  await flags.connect();

  runApp(
    SidekickProvider(client: flags, child: const MyApp()),
  );
}

API Reference

SidekickClient

final client = SidekickClient(
  serverUrl: String,     // required — base URL of your Sidekick server
  sdkKey: String?,       // optional — for authenticated servers
  reconnectDelay: Duration(seconds: 3), // optional
);

client.connect(): Future<void>

Connects to the SSE stream and waits for the initial flag bootstrap to complete. Call this before calling isEnabled().

client.isEnabled(flagKey, userKey, attributes): bool

Synchronous flag evaluation via FFI. No async/await needed.

final enabled = client.isEnabled(
  'new-onboarding',
  userId,
  {'plan': 'pro', 'country': 'US'},
);

client.disconnect(): void

Closes the SSE connection and releases native resources.

Usage with Provider

// main.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:sidekick_flutter/sidekick_flutter.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  final flags = SidekickClient(
    serverUrl: const String.fromEnvironment('SIDEKICK_URL'),
    sdkKey: const String.fromEnvironment('SIDEKICK_KEY'),
  );
  await flags.connect();

  runApp(
    Provider<SidekickClient>.value(
      value: flags,
      child: const MyApp(),
    ),
  );
}

// feature_screen.dart
import 'package:provider/provider.dart';
import 'package:sidekick_flutter/sidekick_flutter.dart';

class FeatureScreen extends StatelessWidget {
  const FeatureScreen({super.key, required this.user});
  final User user;

  @override
  Widget build(BuildContext context) {
    final flags = context.read<SidekickClient>();
    final showNewUI = flags.isEnabled(
      'new-feature-screen',
      user.id,
      {'plan': user.plan},
    );

    return showNewUI ? const NewFeatureScreen() : const LegacyFeatureScreen();
  }
}

Usage with Riverpod

// providers.dart
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:sidekick_flutter/sidekick_flutter.dart';

final sidekickProvider = Provider<SidekickClient>((ref) {
  throw UnimplementedError('Override in ProviderScope');
});

// main.dart
void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  final flags = SidekickClient(serverUrl: '...');
  await flags.connect();

  runApp(
    ProviderScope(
      overrides: [
        sidekickProvider.overrideWithValue(flags),
      ],
      child: const MyApp(),
    ),
  );
}

// In a widget
final flags = ref.read(sidekickProvider);
final enabled = flags.isEnabled('my-flag', userId, {});

Platform Support

Platform	Status
Android (arm64-v8a)	Supported
Android (armeabi-v7a)	Supported
Android (x86_64)	Supported
iOS (arm64)	Supported
iOS Simulator	Supported
macOS	Supported
Linux	Supported
Windows	Supported

Building from Source

If you need to build the native library from source:

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Build for Android
rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android
cargo build --release --target aarch64-linux-android

# Build for iOS
rustup target add aarch64-apple-ios x86_64-apple-ios
cargo build --release --target aarch64-apple-ios