@brainstack/inject

@brainstack/inject

A lightweight dependency injection library for JavaScript and TypeScript, designed to facilitate dependency management and injection in your projects.

Installation

You can install the package using npm:

npm install @brainstack/inject

Usage

Import the inject function and use it to create a dependency container. You can then register, get, and search for dependencies in the container.

Importing

import { inject } from '@brainstack/inject';

Creating a Dependency Container

const container = inject();

Registering a Dependency

interface Logger {
  log(message: string): void;
}

class ConsoleLogger implements Logger {
  log(message: string) {
    console.log(message);
  }
}

const logger = new ConsoleLogger();

const unregister = container.register<Logger>('logger', logger);

Getting a Dependency

const retrievedLogger = container.get<Logger>('logger');
retrievedLogger.log('Hello, world!');

Examples

Example 1: Registering and Retrieving a Logger Service

import { inject } from '@brainstack/inject';

const container = inject();

interface Logger {
  log(message: string): void;
}

class ConsoleLogger implements Logger {
  log(message: string) {
    console.log(message);
  }
}

const logger = new ConsoleLogger();

container.register<Logger>('logger', logger);

const retrievedLogger = container.get<Logger>('logger');
retrievedLogger.log('Hello, world!');

In this example, we define a Logger interface and create a ConsoleLogger class that implements this interface. We then register an instance of ConsoleLogger with the ID 'logger' in the dependency container. Finally, we retrieve the logger service using the get method and use it to log a message.

Example 2: Registering and Searching for Database Connections

import { inject } from '@brainstack/inject';

const container = inject();

interface DatabaseConnection {
  connect(): void;
  disconnect(): void;
}

class MySQLConnection implements DatabaseConnection {
  connect() {
    console.log('Connecting to MySQL database...');
  }

  disconnect() {
    console.log('Disconnecting from MySQL database...');
  }
}

class PostgreSQLConnection implements DatabaseConnection {
  connect() {
    console.log('Connecting to PostgreSQL database...');
  }

  disconnect() {
    console.log('Disconnecting from PostgreSQL database...');
  }
}

const mysqlConnection = new MySQLConnection();
const postgresConnection = new PostgreSQLConnection();

container.register<DatabaseConnection>('mysql', mysqlConnection);
container.register<DatabaseConnection>('postgres', postgresConnection);

const searchResults = container.search<DatabaseConnection>('SQL');
searchResults.forEach((connection) => {
  connection.connect();
  connection.disconnect();
});

In this example, we define a DatabaseConnection interface and create two implementations: MySQLConnection and PostgreSQLConnection. We then register instances of these connections with the IDs 'mysql' and 'postgres' in the dependency container. Finally, we use the search method to find all database connections with 'SQL' in their IDs and connect and disconnect from each of them.

These examples demonstrate how to use the @brainstack/inject library to manage and inject dependencies in a TypeScript project.

API

inject()

Creates a new dependency container.

Returns: Dependency container object with methods.

register<T>(id: string, instance: T): () => void

Registers a new dependency in the container.

• id: The ID of the dependency.
• instance: The instantiated object of the dependency.

Returns: A function to unregister the API section of the README.md file:

get<T>(id: string): T | undefined

Gets a dependency from the container by its ID.

• id: The ID of the dependency.

Returns: The retrieved dependency or undefined if not found.

Contributing

Contributions are welcome! If you would like to contribute to this module, please follow these guidelines:

Fork the repository Create a new branch for your changes Make your changes and commit them with descriptive commit messages Push your changes to your fork Submit a pull request

License

This module is released under the MIT License.

This updated README.md file includes type annotations for TypeScript in the examples and API section, as requested.