Plugins

InversifyJS provides a plugin system that allows you to extend the container's functionality. Plugins can add new methods to the container, hook into the container's lifecycle, and interact with the container's internal services.

Creating a Plugin

danger

Plugins are, at the moment, an experimental feature and may change in future releases. Use them at your own risk.

To create a plugin, you need to extend the Plugin class from @inversifyjs/plugin and implement the load method. The load method receives a PluginApi object that allows the plugin to define new methods on the container and hook into the container's resolution process.

import { Plugin, PluginApi, PluginContext } from '@inversifyjs/plugin';
import { Container } from 'inversify';

// Extend the container with plugin defined methods
declare module 'inversify' {
  interface Container {
    myMethod(...args: any[]): string;
  }
}

class MyPlugin extends Plugin<Container> {
  public load(api: PluginApi): void {
    // Define a new method on the container
    api.define('myMethod', (...args) => {
      // Implementation of the method
      return 'Result of myMethod';
    });

    // Hook into the container's plan phase
    api.onPlan((options, result) => {
      // Do something with the plan result
      console.log(`Planning resolution for ${String(options.serviceId)}`);
    });
  }
}

Plugin Context

When a plugin is created, it receives a container instance and a plugin context. The plugin context provides access to the container's internal services:

• activationService: Manages the activation handlers for services (binding activation is set in the binding).
• bindingService: Manages the bindings in the container.
• deactivationService: Manages the deactivation handlers for services (binding deactivation is set in the binding).
• planResultCacheService: Manages the cache of plan results.

These services allow plugins to interact with the container's core functionality and provide advanced extensions.

Registering a Plugin

To use a plugin, you need to register it with the container using the register method:

const container = new Container();
container.register(MyPlugin);

Once registered, the plugin can add methods to the container, hook into the container's lifecycle, and modify the container's behavior.

Plugin API

The PluginApi interface provides the following methods:

define

define(name: string | symbol, method: (...args: any[]) => unknown): void

Defines a new method on the container. The method will be available on the container instance after the plugin is registered.

onPlan

onPlan(handler: (options: GetPlanOptions, result: PlanResult) => void): void

Registers a handler that is called when the container plans a resolution. This can be used to modify the resolution plan or perform additional actions during the resolution process.

Plugins provide a clean way to extend InversifyJS without modifying its core code, allowing for modular and maintainable extensions.