ts-nest
v0.0.9
Published
NodeJS dependency injection inspired by Angular
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Hierarchical NodeJS dependency injection inspired by Angular
Super lightweight (2kb) library for creating dependency trees in NodeJS applications inpired by Angular. It is build on top of inversify. See this library in action with this stackblitz demo.
Installation
Add the package to your project
npm i --save ts-nest
# or
yarn add ts-nest
Import the decorators with
import { NestModule, Component, Injectable, Inject } from 'ts-nest'
Usage
Create a NestModule
as application entrypoint and import all the
wanted child modules, which are NestModule
s themselves.
@NestModule({
imports: [ AuthModule, HttpModule ],
declarations: [ AppComponent ],
providers: [ AuthService ],
exports: [ ]
})
export class AppModule {}
Bootstrap your application by simply contructing it
const app = new AppModule();
There are two other types of objects in this dependency tree, Component
s and
Injectable
s. Components can be created like follows.
@Component()
export class AppComponent {
constructor (@Inject(AuthService) authService: AuthService) {}
}
As you may have recognized, the constructor receives an Inject
ed parameter. This
parameter can be provided in your NestModule
, like it is done in the first listing.
The AuthService
is decorated by an @Injectable()
decorator
@Injectable()
export class AuthService {}
When it is provided, the application knows about it, but does not directly create an instance. It
gets instanciated when an @Inject(serviceIdentifier)
is used as a constructor parameter in the
same or a childs containers class.
The DI system is hierarchical. So the class provided in the parent module will also be available in all its children (with a single object instance).
Cheatsheet
Decorators
| Decorator | Description | Parameters | Return value |
| ---------------------------- | ------------------- | ----------------- | -------------------- |
| @NestModule()
| Creates a container where the classes are stored, imports child-NestModules | config: { imports?: any[], declarations?: any[], providers?: any[], exports?: any[] } | Returns a custom decorator where a container object is created in the constructor |
| @Injectable()
| Make class bindable to an NestModules container | - | Inversify @injectable() |
| @Component()
| Make class bindable to an NestModules container | - | Inversify @injectable() |
| @Inject(serviceIdentifier)
| Let the DI know that a class instance is needed, if not exist, create class | serviceIdentifier | - |
NestModule parameters
| Input parameter | Description |
| ---------------------------- | -------------------------------- |
| imports | Creates an instance of the imported NestModule()
, reads the exports parameter of the instantiated object and stores the exports in its own container. The instance is handled as a child of this module, so Inject()s will work in the child even if the child does not contain the instance itself, but its parent. |
| declarations | Binds @Component()
decorated classes to the container and after creating all imports it directly creates an instance. |
| providers | Binds @Injectable()
decorated classes to the container |
| exports | Binds @Injectable()
or @Component()
decorated classes to the parents container |
Dependencies
Get in touch
Hi, I am Felix, Angular developer and NgRX contributor
If you like this library, think about giving it a star or follow me on twitter or github.