An implementation of the flutter_ioc package using the popular GetIt service locator as backing IoC container.

Features

The following features are supported:

• Register factory methods to return a new instance everytime one is requested.
• Register lazy singletons which are constructed the first time they are requested but reuse the instance for subsequent requests.
• Register an instance as singleton.
• Use scopes to manage different lifetimes.

Important: if you are integrating flutter_ioc in a Dart or Flutter library please make sure to only depend on the flutter_ioc package.

Getting started

To start using the flutter_ioc_get_it package add it as a dependency in the pubspec.yaml file running the following command:

With Dart:

dart pub add flutter_ioc_get_it

With Flutter:

flutter pub add flutter_ioc_get_it

Usage

First make sure to import the flutter_ioc_get_it library:

import 'package:flutter_ioc_get_it/flutter_ioc_get_it.dart';

Register specific implementation

Once the library is imported, the GetItContainer should be registered as the implementation to use with the IocContainer library.

Important: the registration step is not necessary when developing a Dart or Flutter library. It would be the responsibility of the consuming application to handle the registration. This will prevent tightly coupling in your library.

Note that it is good practice to explain the dependency in the documentation of your library and inform other developers they need to register a specific implementation of the flutter_ioc interface.

It is important that the registration is done before the first time the IocContainer.container instance is accessed. To be sure this is done before the IocContainer.container field is accessed, call the GetItContainer.register() method as one of the first lines in your main function:

void main() {
  // Register the `GetItIocContainer` as the inversion of control 
  // implementation to be used.
  GetItIocContainer.register();

  /// Continue with the rest of your application code.
  ...
}

Using the IocContainer library

Now the flutter_ioc library can be accessed through the IocContainer.container field. Below are some examples showing the diffent ways objects can be registered and retrieved with the inversion of control container.

The samples shown below will be referencing a very simple Counter class that is used to demostrate the different ways to register and retrieve objects to and from the IocContainer.container. Although the implementation of this class in not relevant at all it could look something like this:

class Counter {
    Counter({this.count = 0});

    int count;

    void increment() => count++;
}

For a working example of the snippets below, checkout the example demo application.

To register the Counter class with the IocContainer.container and have it return a new instance each time one is requested, use the registerFactory method:

// Register a factory method to create a new instance of Counter.
IocContainer.container.registerFactory<Counter>(() => Counter());

// Retrieve a new instance of Counter.
final Counter counter = IocContainer.container.get<Counter>();

To register multiple versions of the same type specify a name:

// Register a factory method to create a new instance of Counter
// starting at 0.
IocContainer.container.registerFactory<Counter>(
    () => Counter(),
    instanceName: 'zero-based-counter');
// Register a factory method to create a new instance of Counter
// starting at 42.
IocContainer.container.registerFactory<Counter>(
    () => Counter(count: 42),
    instanceName: '42-based-counter');

// Retrieve a new instance of the Counter starting at 0.
final Counter zeroCounter = IocContainer.container.get<Counter>(instanceName: 'zero-based-counter');
// Retrieve a new instance of the Counter starting at 42.
final Counter forthyTwoCounter = IocContainer.container.get<Counter>(instanceName: '42-based-counter');

To register the Counter class as a singleton that is only created once it is accessed for the first time use the registerLazySingleton method:

// Register a factory method to create singleton instance of Counter.
IocContainer.container.registerLazySingleton<Counter>(() => Counter());

// Retrieve the singleton instance of Counter.
final Counter counter = IocContainer.container.get<Counter>();

To register multiple versions of the same type as lazily initialized singleton, specify a name:

// Register a factory method to create a singleton of Counter
// starting at 0.
IocContainer.container.registerLazySingleton<Counter>(
    () => Counter(),
    instanceName: 'zero-based-counter');
// Register a factory method to create a singleton of Counter
// starting at 42.
IocContainer.container.registerLazySingleton<Counter>(
    () => Counter(count: 42),
    instanceName: '42-based-counter');

// Retrieve the singleton instance of the Counter starting at 0.
final Counter zeroCounter = IocContainer.container.get<Counter>(instanceName: 'zero-based-counter');
// Retrieve the singleton instance of the Counter starting at 42.
final Counter forthyTwoCounter = IocContainer.container.get<Counter>(instanceName: '42-based-counter');

To register the Counter class as a singleton that is already initialized use the registerSingleton method:

// Register an instance of Counter that will be treated as singleton.
IocContainer.container.registerSingleton<Counter>(Counter());

// Retrieve the singleton instance of Counter.
final Counter counter = IocContainer.container.get<Counter>();

To register multiple singleton versions of the same type:

// Register an instance of Counter starting at 0.
IocContainer.container.registerSingleton<Counter>(
    Counter(),
    instanceName: 'zero-based-counter');
// Register an instance of Counter starting at 42.
IocContainer.container.registerSingleton<Counter>(
    Counter(count: 42),
    instanceName: '42-based-counter');

// Retrieve the singleton instance of the Counter starting at 0.
final Counter zeroCounter = IocContainer.container.get<Counter>(instanceName: 'zero-based-counter');
// Retrieve the singleton instance of the Counter starting at 42.
final Counter forthyTwoCounter = IocContainer.container.get<Counter>(instanceName: '42-based-counter');