Function OnEvent

OnEvent(channel: string, event: string): MethodDecorator
Method decorator: handle a specific event on a specific channel.

Receives (payload, event) when the named event arrives on the channel; the connection is connectionOf(event).
Parameters
- channel: string
  The channel to listen on.
- event: string
  The event name to handle.
Returns MethodDecorator
A method decorator.
Example
```
@RealtimeGateway()
export class Chat {
  @OnEvent('room:1', 'message') onMessage (payload, event) { ... }
}
```