Channels

A channel is a transport: it takes a notification and delivers it over one medium — an email, a persisted row, a websocket push, a Slack message. A notification declares a channel by annotating a payload method with the channel's handle (@Mail(), @Database(), …); the channels are then inferred, and each channel reads that one to<Channel>() method for its payload.

For the conceptual split between channels (where it goes) and dispatchers (when it goes), see Channels vs. dispatchers.

Built-in channels

Each channel ships as its own package, so you only pull in what you send. The handle is both the method decorator that declares a payload (@Mail()) and a type-safe token you can return from via() — see Notifications.

Registration is just an import

There is no channels array to maintain. Each *ChannelModule.forRoot() provides a ChannelDriver, and the core finds it through Nest's DiscoveryService at startup. Import the module once in your root module and the channel is live — usable from any notification via its decorator handle.

import { NotificationsModule } from '@dudousxd/nestjs-notifications-core';
import { MailChannelModule } from '@dudousxd/nestjs-notifications-mail';
import { SlackChannelModule } from '@dudousxd/nestjs-notifications-slack';

@Module({
  imports: [
    NotificationsModule.forRoot(),
    MailChannelModule.forRoot({ from: 'no-reply@example.com' }),
    SlackChannelModule.forRoot({ webhookUrl: process.env.SLACK_WEBHOOK_URL }),
  ],
})
export class AppModule {}

Every channel module is global: true by default, so a single registration in the root module makes it discoverable app-wide. Set global: false to scope it to the importing module.

When a payload method is missing

If via() routes a notification to a channel but the notification doesn't implement that channel's method, the channel throws a MissingChannelMethodError at send time:

Notification "InvoicePaid" is routed to the "mail" channel but does not implement
toMail(). Implement it to define the channel payload.

Implement the channel's notification interface (MailNotification, SlackNotification, …) to turn that runtime error into a compile-time one.

Build your own

Need a channel that isn't built in? A channel is just a class with a channel name and a send() method. See Writing a custom channel.