Wyr

Pronounced: wire
Wyr is a zero-crap, zero-dependency, lightweight, and typesafe dependency injection framework for TypeScript. It’s designed to be simple yet powerful, with full support for asynchronous bindings.

Features

• Typesafe: Enjoy TypeScript’s type safety when defining and retrieving dependencies.
• Async Bindings: First class support for async initialization and parallelization of initialization.
• Thread-safe: Modules are immutable and can be shared safely.

Installation

To install Wyr, run:

npm install --save wyr-ts

Core concepts

Modules

A Module is where bindings are defined. You can create a module using Wyr.module(), which will create an empty module. Modules are lightweight, immutable, and can be merged with other modules to combine bindings.

const userModule = Wyr.module()
    .bind(UserService.key).toClass([UserRepo.key,UserEventEmitter.key],DefaultUserService)
    .bind(UserEventEmitter.key).toFun([KafkaFactory.key,DefaultUserEventEmitter.Config.key],createUserEventEmitter)
    .bind(UserRepo.key).toClass([MongoDatabase.key,MongoUserRepo.Config.key],MongoUserRepo)

Containers

A Container is created from a module and is used to initialize and retrieve dependencies. Once you've defined bindings in multiple modules, you can get a container from it, to access the bound dependencies. You cannot bind dependencies to a container, they have to be bound to a module.

const container = Wyr.container(userModule,mongoModule,kafkaModule,httpModule)
//or
const container = userModule.mergedWith(mongoModule).mergedWith(kafkaModule).mergedWith(httpModule).asContainer()

Binding keys

A Bindking Key is a unique identifier for each dependency.. You can create them using Symbol and a type annotation which ensures uniqueness and type safety

namespace UserService{
    const key:BindingKey<UserService> = Symbol('UserService')
}

Bindings

A Binding connects a binding key to a dependency (ie, a way to build it using other dependencies). You can bind a key to a dependency using module.bind(key).toClass or module.bind(key).toFun or module.bind(key).toValue. Modules are immutable, so whenever you bind something, it will return a new module with the new binding in it. So it's important you chain bindings.

const userModule = Wyr.module()
    .bind(UserService.key).toClass([UserRepo.key,UserEventEmitter.key],DefaultUserService)
    .bind(UserEventEmitter.key).toFun([KafkaFactory.key,DefaultUserEventEmitter.Config.key],createUserEventEmitter)
    .bind(UserRepo.key).toClass([MongoDatabase.key,MongoUserRepo.Config.key],MongoUserRepo)

Retrieving dependencies.

You can retrieve dependencies from a container using the .get method. this method takes a key, or a tuple of keys, and will return a promise with the dependency, or a tuple of dependencies. Tuple semantics were added to be able to leverage parallelization of initialization.

const userService = await container.get(UserService.key) 
// OR
const [userService,kafkaFactory] = await container.get([UserService.key,KafkaFactory.key])

License

Wyr is licensed under the MIT License.