flutter_simple_dependency_injection

A simple dependency injection plugin for Flutter.

This implementation does not rely on the dart reflection apis (mirrors) and favours a simple factory based approach. This increases the performance and simplicity of this implementation.

  • Support for multiple injectors (useful for unit testing or code running in isolates)
  • Support for types and named types
  • Support for singletons
  • Support simple values (useful for configuration parameters like api keys or urls)

Any help is appreciated! Comment, suggestions, issues, PR's!

Getting Started

In your flutter project add the dependency:

dependencies:
  ...
  flutter_simple_dependency_injection: any

For help getting started with Flutter, view the online documentation.

Usage example

Import flutter_simple_dependency_injection

import 'package:flutter_simple_dependency_injection/injector.dart';

Injector Configuration

As this injector relies on factories rather than reflection (as mirrors in not available in Flutter) each mapped type needs to provide a factory function. In most cases this can just be a simple new object returned function. In slightly more advanced scenarios where the type to be created relies on other types an injector instances is passed into the factory function to allow the type of be created to get other types it depends on (see below for examples).

import 'package:flutter_simple_dependency_injection/injector.dart';

void main() {
  final injector = Injector.getInjector();
  injector.map<Logger>((i) => new Logger(), isSingleton: true);
  injector.map<String>((i) => "https://api.com/", key: "apiUrl");
  injector.map<SomeService>((i) => new SomeService(i.get<Logger>(), i.get<String>("apiUrl")));
  injector.map<SomeGenericType<String>>((i) => new SomeGenericType("Hello"));
  injector.map<SomeGenericType<int>>((i) => new SomeGenericType(42));

  injector.get<SomeService>().doSomething();
  print(injector.get<SomeGenericType<String>>().propertyOfT) // prints "Hello";
  print(injector.get<SomeGenericType<int>>().propertyOfT) // prints 42;

  // get an instace of each of the same mapped types
  injector.map<SomeType>((injector) => new SomeType("0"));
  injector.map<SomeType>((injector) => new SomeType("1"), key: "One");
  injector.map<SomeType>((injector) => new SomeType("2"), key: "Two");
  final instances = injector.getAll<SomeType>();
  print(instances.length); // prints '3'

  // passing in additional arguments when getting an instance
  injector.mapWithParams<SomeType>((i, p) => new SomeType(p["id"]));
  final instance = injector.get<SomeType>(additionalParameters: { "id": "some-id" });
  print(instance.id); // prints 'some-id'
}

class Logger {
  void log(String message) => print(message); 
}

class SomeService {
  final Logger _logger;
  final String _apiUrl;

  SomeService(this._logger, this._apiUrl);

  void doSomething() {
    _logger.log("Doing something with the api at '$_apiUrl'");
  }
}

class SomeGenericType<T> {
  T propertyOfT;
  SomeService(this.propertyOfT);
}

class SomeType {
  final String id;
  SomeType(this.id);
}

Multiple Injectors

The Injector class has a static method getInjector that by default returns the default instance of the injector. In most cases this will be enough. However, you can pass a name into this method to return another isolated injector that is independent from the default injector. Passing in a new injector name will create the injector if it has not be retrieved before. To destroy isolated injector instances call their dispose method.

  final defaultInjector = Injector.getInjector();
  final isolatedInjector = Injector.getInjector("Isolated");

Libraries

flutter_simple_dependency_injection