ts-nest
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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](http://inversify.io/). See this library in action with this
[stackblitz demo](https://stackblitz.com/edit/ts-nest).
[](https://travis-ci.org/ngfelixl/ts-nest)
[](https://coveralls.io/github/ngfelixl/ts-nest?branch=master)
[](https://badge.fury.io/js/ts-nest)
[](https://github.com/prettier/prettier)
[](https://gitter.im/ts-nest/)
## Installation
Add the package to your project
```bash
npm i --save ts-nest
# or
yarn add ts-nest
```
Import the decorators with
```typescript
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.
```typescript
export class AppModule {}
```
Bootstrap your application by simply contructing it
```typescript
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.
```typescript
export class AppComponent {
constructor ( 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 `` decorator
```typescript
export class AuthService {}
```
When it is provided, the application knows about it, but does not directly create an instance. It
gets instanciated when an `` 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 |
| ---------------------------- | ------------------- | ----------------- | -------------------- |
| `` | 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 |
| `` | Make class bindable to an NestModules container | - | Inversify |
| `` | Make class bindable to an NestModules container | - | Inversify |
| `` | 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 `` decorated classes to the container and after creating all imports it directly creates an instance. |
| providers | Binds `` decorated classes to the container |
| exports | Binds `` or `` decorated classes to the parents container |
## Dependencies
- [inversify](http://inversify.io/)
- [reflect-metadata](https://github.com/rbuckton/reflect-metadata)
## Get in touch
[](https://twitter.com/intent/follow?screen_name=ngfelixl)
[](https://github.com/ngfelixl)
[](https://stackoverflow.com/users/8808496/ngfelixl)
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.