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Dice

Lightweight dependency injection framework for Dart.

Getting Started

Dice consists of two parts. * Modules containing your class registrations. * Injectors that uses the Module to inject instances into your code.

The following example should get you startd:

1. Add the Dice to your pubspec.yaml and run pub install

    dependencies:
      dice: any

2. Create some classes and interfaces to inject

	class BillingServiceImpl implements BillingService {
	  @inject
	  CreditProcessor _processor;
	  
	  Receipt chargeOrder(Order order, CreditCard creditCard) {
	    if(!_processor.validate(creditCard)) {
	      throw new ArgumentError("payment method not accepted");
	    }
	    // :
	  }
	}

3. Register types and classes in a module

	class ExampleModule extends Module {
	  configure() {
	    // register [CreditProcessor] as a singleton
	    register(CreditProcessor).toInstance(new CreditProcessorImpl());
	    // register [BillingService] so a new version is created each time its requested
	    register(BillingService).toType(BillingServiceImpl);
	  }
	}

4. Run it

    import "package:dice/dice.dart";
	main() {
	  	var injector = new Injector(new ExampleModule());
	  	var billingService = injector.getInstance(BillingService);
	  	var creditCard = new CreditCard("VISA");
	  	var order = new Order("Dart: Up and Running");
	  	billingService.chargeOrder(order, creditCard);
	}

for more information see the full example here.

Dependency Injection with Dice

You can use the @inject annotation to mark objects and functions for injection the following ways:

  • Injection of public and private fields (object/instance variables)
	class MyOtherClass {
    	@inject
      	SomeClass field;
      	@inject
      	SomeOtherClass _privateField;
   	}
  • Injection of constructor parameters
	class MyClass {
 		@inject
 		MyClass(this.field);
 		
 		MyOtherClass field;
 	}
  • Injection of public and private setters
	class SomeClass {
      	@inject
      	set value(SomeOtherClass val) => _privateValue = val;
      	
      	@inject
      	set _value(SomeOtherClass val) => _anotherPrivateValue = val;

      	SomeOtherClass _privateValue, _anotherPrivateValue;
	}

The injected objects are configured by extending the Module class and using one its register functions

  • register(MyType).toInstance(object) register type MyType to existing object (singleton injections)
  • register(MyType).toType(MyType) register type MyType to an (possible alternative) class implementing it.
  • register(MyTypedef).toFunction(function) register a typedef to a function matching it.
  • register(MyType).toBuilder(() => new MyType()) register MyType to function that can build instances of it

Named Injections

Dice supports named injections by using the @Named annotation. Currently this annotation works everywhere the @inject annotation works, except for constructors.

	class MyClass {
      	@inject
      	@Named('my-special-implementation')
      	SomeClass _someClass;
   	}

The configuration is as before except you now use method namedRegister in your Module implementation.

  • namedRegister(MyType, "my-name").toInstace(object)
  • namedRegister(MyType, "my-name").toType(MyType)
  • namedRegister(MyTypedef, "my-name").toFunction(function)
  • namedRegister(MyType, "my-name").toBuilder(() => new MyType())

Advanced Features

  • Get instances directly Instead of using the @inject annotation to resolve injections you can use the injectors getInstance method
   MyClass instance = injector.getInstance(MyClass);
  • Get named instances directly Instead of using the @Named annotation to resolve named injections you can use the injectors getNamedInstance method
   MyType instance = injector.getNamedInstance(MyType, "my-name");
  • To register and resole configuration values You can use named registrations to inject configuration values into your application.
	class TestModule extends Module {
    	configure() {
			namedRegister(String, "web-service-host").toInstace("http://test-service.name");
		}
	}
	
	// application code
	String get webServiceHost => injector.getNamedInstance(String, "web-service-host");
  • Registrering dependencies at runtime You can register dependencies at runtime by accessing the module property on the Injector instance.
	 injector.module.register(User).toInstance(user);
	 :
	 var user = injector.getInstance(User);
  • Using multiple modules You can compose mudules using the Injector.fromModules constructor
	class MyModule extends Module {
    	configure() {
			register(MyClass).toType(MyClass);
		}
	}
	
	class YourModule extends Module {
    	configure() {
			register(YourClass).toType(YourClass);
		}
	}
	
	var injector = new Injector.fromModules(new MyModule(), new YourModule());
	var myClass = injector.getInstance(MyClass);
	var yourClass = injector.getInstance(YourClass);

Libraries

dice

Lightweight dependency injection framework for Dart.