Wired-up

Painless dependency injection for TypeScript

Tired of endless boilerplate code for wiring up dependencies in TypeScript? Wired-up provides a clean, simple API for injecting services using constructor and parameter injection powered by TypeScript metadata reflection.

Installation

npm i wired-up
yarn add wired-up
pnpm i wired-up

Usage

await Container.startScope(async () => {
  const injectedFn = await Container.instance.resolve(excellentFunction);
  await injectedFn();
});

Example

Let's start with setting up an abstract representation of the services we'll need.

export interface ILogger {
  log(message: string): void;
}

export interface IDatabase {
  query(sql: string, params: any[]): Promise<any[]>;
}

Next, let's create the concrete implementations. For the logger, let's assume we need to call an outer function to retrieve the instance.

export async function createLogger(): Promise<ILogger> {
  return {
    log: (message: string) => {
      console.log(message);
    }
  }
}

The database is a bit different, it's safe to assume we'll need to setup and teardown.

export async function createConnection(): Promise<IDatabase> {
  // Instantiate the db/connection.
  return await db.connect();
}

export async function closeConnection(connection: any) {
  console.log('Closing connection');
}

Now let's assume we have a function that requires both the logger and the database.

export const deeperFunction = async (logger: ILogger, db: IDatabase): Promise<DeeperFn> => async (count: number) => {
  logger.log(`Logger called with count: ${count}`);
  db.query('SELECT * FROM foo', []);
}

Let's also say we have an outer level function that doesn't know/care about the logger or database, but needs to call the deeperFunction we just defined.

export const excellentFunction = (deeperFunction: DeeperFn) => () => {
  deeperFunction(1);
}

Finally, let's set up out context.

import * as db from './core/db';
import * as logger from './core/logger';
import { deeperFunction } from './core/deeper';

await Container.register()
  .singleton('db', db.createConnection, db.closeConnection)
  .scoped('logger', logger.createLogger)
  .transient('deeperFunction', deeperFunction)
  .build();

We can then resolve the dependencies and run the outer function without needing to worry about a significant amout of additional boiler plate.

await Container.startScope(async () => {
  const injectedFn = await Container.instance.resolve(excellentFunction);
  await injectedFn();
});

Contributions

We welcome contributions! Please read the contribution guidelines to get started.

Let me know if you would like me to modify or expand this example repository description in any way!