tioc

TIOC - Type Inversion of Control

A simple Inversion of Control library for JavaScript.

Features

• 3 different scopes:
  • Singleton - Instantiated once per ServiceRegistry
  • Scoped - Instantiated once per ServiceProvider
  • Transient - Instantiated every time when requested
• Simple, only includes what's necessary
• Tiny, if you care about size, it's only around ~1kb (minified)

Usage

Adding services

import { ServiceRegistry } from "tioc";

class Service {
  // ...
}

ServiceRegistry.create()
  // Adding a simple service
  .add("singleton", "myService", () => new Service())

  // Alternative way to write it!
  .addSingleton("foo", () => new Service())
  .addScoped("bar", () => new Service())
  .addTransient("baz", () => new Service());

Requesting services

import { ServiceRegistry } from "tioc";

class Service {
  // ....
}

// Register a new instance of Service to the key "foo"
const registry = ServiceRegistry.create()
  .addSingleton("foo", () => new Service());

// Start a new scope. This will give you a ServiceProvider
const provider = registry.scope();

// Retreive the service by the key, "foo"
const service = provider.foo();

Dependent services

tioc allows services to depend on another. Factory functions are given a provider instance that they can use to get previously registered services.

import { ServiceRegistry } from "tioc";

class Config {
  // ...
}

class Database {
  constructor(private config: Config) {}
  // ...
}

// ✅ Register the service you want to depend on first, and then use it!
ServiceRegistry.create()
  .addSingleton("config", () => new Config())
  .addSingleton("database", (provider) => new Database(provider.config())); // `provider` is a ServiceProvider, like the one received from `ServiceRegistry.scope()`

// ❌ Doesn't work. Services can't depend on ones that arent registered yet. This prevents cyclic dependencies.
ServiceRegistry.create()
  .addSingleton("database", (provider) => new Database(provider.config())) // Error: Property 'config' does not exist on type '{}'.
  .addSingleton("config", () => new Config());

Async services

It isn't recommended to make your services async, but sometimes there is no way around it. The ServiceRegistry and ServiceProvider are built to allow for async services.

import { ServiceRegistry } from "tioc";

class Exchange {}
class Queue {}

declare class MessageQueue {
  makeExchange(): Promise<Exchange>;
  makeQueue(exchange: Exchange): Promise<Queue>;
}

const registry = ServiceRegistry.create()
  .addSingleton("mq", () => new MessageQueue())
  // Simply return a promise
  .addSingleton("exchange", (provider) => provider.mq().makeExchange())
  // Factory functions are allowed to be async.
  .addSingleton("queue", async (provider) => {
    const exchange = await provider.exchange()
    return await provider.mq().makeQueue(exchange);
  });

const provider = registry.scope();

// Async trickles down into the provider.
// If your factory returns a Promise, your provider will.
const exchange = await provider.exchange();
const queue = await provider.queue();