zone_local 0.1.0

Zone-scoped values. Can be used an alternative to dependency injection.

Introduction

• Zone-local values are similar to "ThreadLocal" values in multi-threading languages like Java. In terms of performance, creating a new Zone is much cheaper than creating a thread. See explanation of zones at dartlang.org.
• This packages optimizes ease and performance of:
  • Getting a zone-scoped value.
  • Setting the default values. You can optionally prevent accidental mutations of default values.
  • Forking the current zone.
• A minimalistic alternative to dependency injection.
  • Introduces a single, easy-to-understand class.
  • No compile-time code generation or other magic.

Example

pubspec.yaml

dependencies:
  zone_local: ^0.1.0

main.dart

import 'package:zone_local/zone_local.dart';

void main() {
  // Configure a zone-local service.
  // The method also prevents later (accidental) modification of the default value.
  GreetingService.zoneLocal.freezeDefaultValue(GreetingService("Hello, world!"));

  // Use the service
  print(GreetingService.zoneLocal.value.greeting);
  // --> Hello, world!

  // Fork a zone with different value
  final forkedZone = GreetingService.zoneLocal.forkZoneWithValue(new GreetingService("Hi, forked zone!"));
  forkedZone.run(() {
    print(GreetingService.zoneLocal.value.greeting);
    // --> Hi forked, zone!
  });
}

class GreetingService {
  static final ZoneLocal<GreetingService> zoneLocal = ZoneLocal<GreetingService>();

  final String greeting;
  GreetingService(this.greeting);
}