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HadesContainer

HadesContainer is where we tell Hades about the services that make up our bot.

It is a wrapper around Inversify.js and exposes largely the same API.

To learn more about dependency injection, check out our guides:

Binding Services​

HadesContainer exposes the bind() method which is used to bind services to the container.

// src/index.ts
const container = new HadesContainer();
container.bind(ILogger).to(ConsoleLogger);

In this case, we told the container that when we request ILogger, we want to get an instance of ConsoleLogger.

Installers​

The constructor for HadesContainer accepts an Inversify interfaces.ContainerOptions object which can be used to configure the container.

Hades adds an additional option called installers which is an array of Installer instances.

The Installer interface exposes a single method called install() which is called when the container is configured.

// src/LoggerInstaller.ts
export class LoggerInstaller implements Installer {
  install(container: Container) {
    container.bind(ILogger).to(ConsoleLogger);
  }
}

This can then be passed to the HadesContainer constructor.

const container = new HadesContainer({
  installers: [new LoggerInstaller()],
});

Installer Functions​

If your installer is simple, you can also pass a function to the installers array.

const container = new HadesContainer({
  installers: [(container) => container.bind(ILogger).to(ConsoleLogger)],
});

Resolving Services​

HadesContainer exposes the get() method which is used to resolve services from the container.

const logger = container.get(ILogger);

In this case, we requested an instance of ILogger from the container and got an instance of ConsoleLogger. This is because we bound ILogger to ConsoleLogger earlier.

Injecting Services​

Services can depend on other services by using the @inject() decorator.

// src/services/SomeService.ts
@injectable()
export class SomeService {
  @inject(ILogger)
  log: ILogger;

  doSomething() {
    this.log.info("Did something!");
  }
}

In this case, SomeService depends on ILogger.

Since we bound ILogger to ConsoleLogger, SomeService will get an instance of ConsoleLogger when it is resolved from the container.