Anchorjs

Dependency injection for Nodejs.

Install

npm install @pyriter/anchorjs

Features

• Seamless imports with your IDE (via typescript)
• Allows named dependency
• Order of $install does not matter
• Infer dependency injection by object type

Usage

Import the $install function to add objects, functions, values to the anchor module

import { $install } from '@pyriter/anchorjs';

declare type Foo = {
  bar: string
};
const myValue: Foo = {
  bar: "foobar"
};

$install<Foo>("foo", {
  provide: () => myValue,
  type: DependencyType.SINGLETON,
});

In a separate module or file use the $inject function to retrieve the desired object, function or value

import { $inject } from '@pyriter/anchorjs';

const foo = $inject<Foo>('foo');
console.log(foo.bar); // prints "foobar" to the console

Using dependency injection to inject data providers

One useful thing about dependency injection is to configure your objects and then have them injected to other objects on creation

import { $install, DependencyType } from '@pyriter/anchorjs';

type Credential = {
  username: string,
  password: string
};

const credentials = {
  username: "username",
  password: "password"
};

type DataSourceProvider = {
  getCredentials: () => Credential
}

$install<DataSourceProvider>('dataStoreProvider', {
  provide: () => new DataSourceProvider(credentials),
  type: DependencyType.FACTORY
});

Then in a separate file, you can create another object that uses these providers without knowing how to set them up

import { $inject } from '@pyriter/anchorjs';

class MyActionController {
  constructor(readonly private dataSourceProvider = $inject<DataSourceProvider>("dataSourceProvider")) {
  }

  public async getCredentials(): Promise<DataItem> {
    return this.dataSourceProvider.getCredentials();
  }
}

Now you can create the MyActionController object without having to know how to create the 2 dataSources

const myActionController = new MyActionController();

API

$install

The $install function takes in 2 arguments: key: string, and props: InjectProps

key

The key is a string value only (at this time)

InjectProps

type InjectProps = {
  provide: () => T,
  type: DependencyType
}

The type is used to determine if the provide function call be called for every $inject (Factory) or should the value be retrieved by a lookup (Singleton). The default behavoir is DependencyType.Factory

$inject

The $inject function is used to retrieve the desired object from the installation step. It takes in the return type and the key

type $inject = (key: string)<T> => T;