injectable #

Injectable is a convenient code generator for get_it. Inspired by Angular DI, Guice DI and inject.dart.

• Installation
• Setup
• Registering factories
• Registering singletons
• Registering asynchronous injectables
• Passing Parameters to factories
• Binding abstract classes to implementations
• Register under different environments
• Using named factories and static create functions
• Registering third party types
• Auto registering $Experimental$

Installation #

dependencies:
  # add injectable to your dependencies
  injectable:
  # add get_it
  get_It:

dev_dependencies:
  # add the generator to your dev_dependencies
  injectable_generator:
  # of course build_runner is needed to run the generator
  build_runner:

Setup #

.1 Create a new dart file and define a global var for your GetIt instance .2 Define a top-level function (lets call it configureDependencies) then annotate it with @injectableInit. .3 Call the Generated func $initGetIt() inside your configure func and pass in the getIt instance.

final getIt = GetIt.instance;

@injectableInit 
void configureDependencies() => $initGetIt(getIt);

Note: you can tell injectable what directories to generate for using the generateForDir property inside of @injectableInit. The following example will only process files inside of the test folder

@InjectableInit(generateForDir: ['test'])
void configureDependencies() => $initGetIt(getIt);

.4 Call configureDependencies() in your main func before running the App

void main() {
 configureDependencies();
 runApp(MyApp());
}

Registering factories #

All you have to do now is annotate your injectable classes with @injectable and let the generator do the work.

@injectable
class ServiceA {}

@injectable
class ServiceB {
    ServiceB(ServiceA serviceA);
}

Run the generator #

Use the [watch] flag to watch the files system for edits and rebuild as necessary.

flutter packages pub run build_runner watch

if you want the generator to run one time and exits use

flutter packages pub run build_runner build

Inside of the generated file #

Injectable will generate the needed register functions for you

final getIt = GetIt.instance;

void $initGetIt(GetIt g, {String environment}) {
  g.registerFactory<ServiceA>(() => ServiceA());
  g.registerFactory<ServiceB>(ServiceA(getIt<ServiceA>()));
}

Registering singletons #

Use the @singleton or @lazySingleton to annotate your singleton classes. Alternatively use the constructor version to pass signalsReady to getIt.registerSingleton(signalsReady) @Singleton(signalsReady: true) >> getIt.registerSingleton(Model(), signalsReady: true) @LazySingleton() >> getIt.registerLazySingleton(() => Model())

@singleton // or @lazySingleton
class ApiProvider {}

Registering asynchronous injectables #

Requires GetIt >= 4.0.0

if you are to make our instance creation async you're gonna need a static initializer method since constructors can not be asynchronous.

class ApiClient {
  static Future<ApiClient> create(Deps ...) async {
    ....
    return apiClient;
  }
}

Now simply annotate your class with @injectable and tell injectable to use that static initializer method as a factory method using the @factoryMethod annotation

@injectable // or lazy/singleton
class ApiClient {
@factoryMethod
  static Future<ApiClient> create(Deps ...) async {
    ....
    return apiClient;
  }
}

injectable will automatically register it as an asynchronous factory because the return type is a Future. Generated Code:

g.registerFactoryAsync<ApiClient>(() => ApiClient.create());

Using a register module (for third party dependencies) #

just wrap your instance with a future and you're good to go

@module
abstract class RegisterModule {
  Future<SharedPreferences> get prefs => SharedPreferences.getInstance();
}

Don't forget to call getAsync() instead of get() when resolving an async injectable

Pre-Resolving the future #

if you want to pre-await the future and register it's resolved value, annotate your async dependencies with @preResolve

@module
abstract class RegisterModule {
  @preResolve
  Future<SharedPreferences> get prefs => SharedPreferences.getInstance();
}

generated code

Future<void> $initGetIt(GetIt g, {String environment}) async {
  final registerModule = _$RegisterModule();
  final sharedPreferences = await registerModule.prefs;
  g.registerFactory<SharedPreferences>(() => sharedPreferences);
  ...
  }

as you can see this will make your initGetIt func async so be sure to await for it

Passing Parameters to factories #

Requires GetIt >= 4.0.0 If you're working with a class you own simply annotate your changing constructor param with @factoryParam, you can have up to two parameters max!

@injectable
class BackendService {
  BackendService(@factoryParam String url);
}

generated code

g.registerFactoryParam<BackendService, String, dynamic>(
    (url, _) => BackendService(url),
  );

Using a register module (for third party dependencies) #

if you declare a module member as a method instead of a simple accessor, injectable will treat it as a factory method, meaning it will inject it's parameters as it would with a regular constructor. The same way if you annotate an injected param with @factoryParam injectable will treat it as a factory param.

@module
abstract class RegisterModule {
   BackendService getService(ApiClient client, @factoryParam String url) => BackendService(client, url);
}

generated code

g.registerFactoryParam<BackendService, String, dynamic>(
      (url, _) => registerModule.getService(g<ApiClient>(), url));

Binding abstract classes to implementations #

Use the 'as' Property inside of Injectable(as:..) to pass an abstract type that's implemented by the registered dependency

@Injectable(as: Service) //Singleton(as: Service) ..
class ServiceImpl implements Service {}

Generated code for the Above example

g.registerFactory<Service>(() => ServiceImpl())

Binding an abstract class to multiple implementations #

Since we can't use type binding to register more than one implementation, we have to use names (tags) to register our instances or register under different environment. (we will get to that later)

@Named("impl1")
@Injectable(as: Service)
class ServiceImpl implements Service {}

@Named("impl2")
@Injectable(as: Service)
class ServiceImp2 implements Service {}

Next annotate the injected instance with @Named() right in the constructor and pass in the name of the desired implementation.

@injectable
class MyRepo {
   final Service service;
    MyRepo(@Named('impl1') this.service)
}

Generated code for the Above example

g.registerFactory<Service>(() => ServiceImpl1(), instanceName: 'impl1')
g.registerFactory<Service>(() => ServiceImpl2(), instanceName: 'impl2')

g.registerFactory<MyRepo>(() => MyRepo(getIt('impl1'))

Auto Tagging #

Use the lower cased @named annotation to automatically assign the implementation class name to the instance name. Then use @Named.from(Type) annotation to extract the name from the type

@named
@Injectable(as: Service)
 class ServiceImpl1 implements Service {}

@injectable
class MyRepo {
   final Service service;
    MyRepo(@Named.from(ServiceImpl1) this.service)
}

Generated code for the Above example

g.registerFactory<Service>(() => ServiceImpl1(), instanceName: 'ServiceImpl1')
g.registerFactory<MyRepo>(() => MyRepo(getIt('ServiceImpl1'))

Register under different environments #

it is possible to register different dependencies for different environments by using @Environment('name') annotation. in the below example ServiceA is now only registered if we pass the environment name to $initGetIt(environment: 'dev')

@Environment("dev")
@injectable
class ServiceA {}

Generated code for the Above example

void $initGetIt({String environment}) {
 // ... other deps
  if (environment == 'dev') {
    _registerDevDependencies();
  }
}

you could also create your own environment annotations by assigning the const constructor Environment("") to a global const var.

const dev = const Environment('dev');
// then just use it to annotate your classes
@dev
@injectable
class ServiceA {}

Usually you would want to register a different implementation for the same abstract class under different environments. to do that pass your environment name to the env property inside of Injectable(env:..) annotation or use @Environment("env") annotation.

@dev
@Injectable(as: Service)
class MockServiceImpl implements Service {}
// or
@Injectable(as: Service, env: Environment.prod)
class RealServiceImpl implements Service {}

Generated code for the Above example

void $initGetIt(GetIt getIt, {String environment}) {
// ..other deps
   //Register dev Dependencies --------
  if (environment == 'dev') {
     g.registerFactory<Service>(() => FakeServiceImpl());
  }
   //Register prod Dependencies --------
  if (environment == 'prod') {
      g.registerFactory<Service>(() => RealServiceImpl());
  }
}

Using named factories and static create functions #

By default injectable will use the default constructor to build your dependencies but, you can tell injectable to use named/factory constructors or static create functions by using the @factoryMethod annotation. .

@injectable
class MyRepository {
  @factoryMethod
  MyRepository.from(Service s);
}

The constructor named "from" will be used when building MyRepository.

g.registerFactory<MyRepository>(MyRepository.from(getIt<Service>()));

or annotate static create functions or factories inside of abstract classes with @factoryMethod

@injectable
abstract class Service {
  @factoryMethod
  static ServiceImpl2 create(ApiClient client) => ServiceImpl2(client);

  @factoryMethod
  factory Service.from() => ServiceImpl();
}

Generated code.

g.registerFactory<Service>(() => Service.create(getIt<ApiClient>()));

Registering third party types #

To Register third party types, create an abstract class and annotate it with @module then add your third party types as property accessors or methods like follows:

@module
abstract class RegisterModule {
  @singleton
  ThirdPartyType get thirdPartyType;

  @prod
  @Injectable(as: ThirdPartyAbstract)
  ThirdPartyImpl get thirdPartyType;
 
}

Providing custom initializers #

In some cases you'd need to register instances that are asynchronous or singleton instances or just have a custom initializer and that's a bit hard for injectable to figure out on it's own, so you need to tell injectable how to initialize them;

@module
abstract class RegisterModule {

 // You can register named premetive types like follows
  @Named("BaseUrl")
  String get baseUrl => 'My base url'
  
  // url here will be injected 
  @lazySingleton
  Dio get dio(@Named('BaseUrl) String url) => Dio(BaseOptions(baseUrl: url));
 
  // same thing works for instances that's gotten asynchronous.
  // all you need to do is wrap your instance with a future and tell injectable how
  // to initialize it
  @preResolve // if you need to  pre resolve the value
  Future<SharedPreferences> get prefs => SharedPreferences.getInstance();
  // Also make sure you await for your configure function before running the App.
 
}

if you're facing even a weirder scenario you can always register them manually in the configure function.

Auto registering $Experimental$ #

Instead of annotating every single injectable class you write, it is possible to use a Convention Based Configuration to auto register your injectable classes, especially if you follow a concise naming convention.

for example you can tell the generator to auto-register any class that ends with Service, Repository or Bloc using a simple regex pattern class_name_pattern: 'Service$|Repository$|Bloc$' To use auto-register create a file with the name build.yaml in the same directory as pubspec.yaml and add

targets:
  $default:
    builders:
      injectable_generator:injectable_builder:
        options:
          auto_register: true
          # auto register any class with a name matches the given pattern
          class_name_pattern:
            "Service$|Repository$|Bloc$"
            # auto register any class inside a file with a
            # name matches the given pattern
          file_name_pattern: "_service$|_repository$|_bloc$"

Problems with the generation? #

Make sure you always Save your files before running the generator, if that does not work you can always try to clean and rebuild.

flutter packages pub run build_runner clean

Support the Library #

• You can support the library by staring it on Github && liking it on pub or report any bugs you encounter.
• also if you have a suggestion or think something can be implemented in a better way, open an issue and lets talk about it.